diff --git a/oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationServerConfigurer.java b/oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationServerConfigurer.java
index e69f0ecf..d2a3cb00 100644
--- a/oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationServerConfigurer.java
+++ b/oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationServerConfigurer.java
@@ -159,11 +159,11 @@ public final class OAuth2AuthorizationServerConfigurer<B extends HttpSecurityBui
 		validateProviderSettings(providerSettings);
 		initEndpointMatchers(providerSettings);
 
-		PasswordEncoder passwordEncoder = getOptionalBean(builder, PasswordEncoder.class);
 		OAuth2ClientAuthenticationProvider clientAuthenticationProvider =
 				new OAuth2ClientAuthenticationProvider(
 						getRegisteredClientRepository(builder),
 						getAuthorizationService(builder));
+		PasswordEncoder passwordEncoder = getOptionalBean(builder, PasswordEncoder.class);
 		if (passwordEncoder != null) {
 			clientAuthenticationProvider.setPasswordEncoder(passwordEncoder);
 		}
diff --git a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProvider.java b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProvider.java
index 148f9ffd..290f73c9 100644
--- a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProvider.java
+++ b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProvider.java
@@ -53,6 +53,7 @@ import org.springframework.util.StringUtils;
  * @see OAuth2ClientAuthenticationToken
  * @see RegisteredClientRepository
  * @see OAuth2AuthorizationService
+ * @see PasswordEncoder
  */
 public class OAuth2ClientAuthenticationProvider implements AuthenticationProvider {
 	private static final OAuth2TokenType AUTHORIZATION_CODE_TOKEN_TYPE = new OAuth2TokenType(OAuth2ParameterNames.CODE);
@@ -75,7 +76,15 @@ public class OAuth2ClientAuthenticationProvider implements AuthenticationProvide
 		this.passwordEncoder = PasswordEncoderFactories.createDelegatingPasswordEncoder();
 	}
 
-	public void setPasswordEncoder(PasswordEncoder passwordEncoder) {
+	/**
+	 * Sets the {@link PasswordEncoder} used to validate
+	 * the {@link RegisteredClient#getClientSecret() client secret}.
+	 * If not set, the client secret will be compared using
+	 * {@link PasswordEncoderFactories#createDelegatingPasswordEncoder()}.
+	 *
+	 * @param passwordEncoder the {@link PasswordEncoder} used to validate the client secret
+	 */
+	public final void setPasswordEncoder(PasswordEncoder passwordEncoder) {
 		Assert.notNull(passwordEncoder, "passwordEncoder cannot be null");
 		this.passwordEncoder = passwordEncoder;
 	}
@@ -100,7 +109,7 @@ public class OAuth2ClientAuthenticationProvider implements AuthenticationProvide
 
 		if (clientAuthentication.getCredentials() != null) {
 			String clientSecret = clientAuthentication.getCredentials().toString();
-			if (!passwordEncoder.matches(clientSecret, registeredClient.getClientSecret())) {
+			if (!this.passwordEncoder.matches(clientSecret, registeredClient.getClientSecret())) {
 				throwInvalidClient();
 			}
 			authenticatedCredentials = true;
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationCodeGrantTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationCodeGrantTests.java
index 3becb364..2bac7ff3 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationCodeGrantTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2AuthorizationCodeGrantTests.java
@@ -45,6 +45,8 @@ import org.springframework.security.config.annotation.web.configuration.OAuth2Au
 import org.springframework.security.config.test.SpringTestRule;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.OAuth2TokenType;
 import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
@@ -388,6 +390,12 @@ public class OAuth2AuthorizationCodeGrantTests {
 				}
 			};
 		}
+
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 
 	@EnableWebSecurity
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2ClientCredentialsGrantTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2ClientCredentialsGrantTests.java
index e478bea1..3663207d 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2ClientCredentialsGrantTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2ClientCredentialsGrantTests.java
@@ -34,6 +34,8 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.config.annotation.web.configuration.OAuth2AuthorizationServerConfiguration;
 import org.springframework.security.config.test.SpringTestRule;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.endpoint.OAuth2ParameterNames;
 import org.springframework.security.oauth2.jose.TestJwks;
@@ -179,5 +181,11 @@ public class OAuth2ClientCredentialsGrantTests {
 		OAuth2TokenCustomizer<JwtEncodingContext> jwtCustomizer() {
 			return jwtCustomizer;
 		}
+
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 }
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2RefreshTokenGrantTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2RefreshTokenGrantTests.java
index 872841ed..8fdf8ecd 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2RefreshTokenGrantTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2RefreshTokenGrantTests.java
@@ -44,6 +44,8 @@ import org.springframework.security.config.annotation.web.configuration.OAuth2Au
 import org.springframework.security.config.test.SpringTestRule;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.OAuth2TokenType;
 import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
@@ -212,5 +214,11 @@ public class OAuth2RefreshTokenGrantTests {
 				}
 			};
 		}
+
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 }
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenIntrospectionTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenIntrospectionTests.java
index 7aa36ded..e26993c5 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenIntrospectionTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenIntrospectionTests.java
@@ -38,6 +38,8 @@ import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.config.annotation.web.configuration.OAuth2AuthorizationServerConfiguration;
 import org.springframework.security.config.test.SpringTestRule;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AbstractOAuth2Token;
 import org.springframework.security.oauth2.core.OAuth2AccessToken;
 import org.springframework.security.oauth2.core.OAuth2RefreshToken;
@@ -242,5 +244,11 @@ public class OAuth2TokenIntrospectionTests {
 		ProviderSettings providerSettings() {
 			return providerSettings;
 		}
+
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 }
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenRevocationTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenRevocationTests.java
index b72b5897..06d9c261 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenRevocationTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OAuth2TokenRevocationTests.java
@@ -35,6 +35,8 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.config.annotation.web.configuration.OAuth2AuthorizationServerConfiguration;
 import org.springframework.security.config.test.SpringTestRule;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AbstractOAuth2Token;
 import org.springframework.security.oauth2.core.OAuth2AccessToken;
 import org.springframework.security.oauth2.core.OAuth2RefreshToken;
@@ -203,6 +205,12 @@ public class OAuth2TokenRevocationTests {
 		JWKSource<SecurityContext> jwkSource() {
 			return jwkSource;
 		}
+
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 
 	@EnableWebSecurity
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcClientRegistrationTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcClientRegistrationTests.java
index 97f20e3c..dead12e1 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcClientRegistrationTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcClientRegistrationTests.java
@@ -41,6 +41,8 @@ import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.config.annotation.web.configuration.OAuth2AuthorizationServerConfiguration;
 import org.springframework.security.config.test.SpringTestRule;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.ClientAuthenticationMethod;
 import org.springframework.security.oauth2.core.OAuth2AccessToken;
@@ -237,5 +239,10 @@ public class OidcClientRegistrationTests {
 			return jwkSource;
 		}
 
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 }
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
index 48941f19..2da8337f 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/authorization/OidcTests.java
@@ -45,6 +45,8 @@ import org.springframework.security.config.annotation.web.configuration.OAuth2Au
 import org.springframework.security.config.test.SpringTestRule;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.OAuth2TokenType;
 import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
@@ -274,6 +276,11 @@ public class OidcTests {
 			};
 		}
 
+		@Bean
+		PasswordEncoder passwordEncoder() {
+			return NoOpPasswordEncoder.getInstance();
+		}
+
 	}
 
 	@EnableWebSecurity
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProviderTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProviderTests.java
index 993b91fb..e7dafac1 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProviderTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/authentication/OAuth2ClientAuthenticationProviderTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 the original author or authors.
+ * Copyright 2020-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,8 @@ import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
 
+import org.springframework.security.crypto.password.NoOpPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.security.oauth2.core.AuthorizationGrantType;
 import org.springframework.security.oauth2.core.ClientAuthenticationMethod;
 import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
@@ -37,8 +39,11 @@ import org.springframework.security.oauth2.server.authorization.client.TestRegis
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 /**
@@ -64,6 +69,7 @@ public class OAuth2ClientAuthenticationProviderTests {
 	private RegisteredClientRepository registeredClientRepository;
 	private OAuth2AuthorizationService authorizationService;
 	private OAuth2ClientAuthenticationProvider authenticationProvider;
+	private PasswordEncoder passwordEncoder;
 
 	@Before
 	public void setUp() {
@@ -71,6 +77,18 @@ public class OAuth2ClientAuthenticationProviderTests {
 		this.authorizationService = mock(OAuth2AuthorizationService.class);
 		this.authenticationProvider = new OAuth2ClientAuthenticationProvider(
 				this.registeredClientRepository, this.authorizationService);
+		this.passwordEncoder = spy(new PasswordEncoder() {
+			@Override
+			public String encode(CharSequence rawPassword) {
+				return NoOpPasswordEncoder.getInstance().encode(rawPassword);
+			}
+
+			@Override
+			public boolean matches(CharSequence rawPassword, String encodedPassword) {
+				return NoOpPasswordEncoder.getInstance().matches(rawPassword, encodedPassword);
+			}
+		});
+		this.authenticationProvider.setPasswordEncoder(this.passwordEncoder);
 	}
 
 	@Test
@@ -88,8 +106,8 @@ public class OAuth2ClientAuthenticationProviderTests {
 	}
 
 	@Test
-	public void constructorWhenPasswordEncoderNullThenThrowIllegalArgumentException() {
-		assertThatThrownBy(() -> authenticationProvider.setPasswordEncoder(null))
+	public void setPasswordEncoderWhenNullThenThrowIllegalArgumentException() {
+		assertThatThrownBy(() -> this.authenticationProvider.setPasswordEncoder(null))
 				.isInstanceOf(IllegalArgumentException.class)
 				.hasMessage("passwordEncoder cannot be null");
 	}
@@ -127,6 +145,7 @@ public class OAuth2ClientAuthenticationProviderTests {
 				.extracting(ex -> ((OAuth2AuthenticationException) ex).getError())
 				.extracting("errorCode")
 				.isEqualTo(OAuth2ErrorCodes.INVALID_CLIENT);
+		verify(this.passwordEncoder).matches(any(), any());
 	}
 
 	@Test
@@ -151,9 +170,11 @@ public class OAuth2ClientAuthenticationProviderTests {
 				.thenReturn(registeredClient);
 
 		OAuth2ClientAuthenticationToken authentication = new OAuth2ClientAuthenticationToken(
-				registeredClient.getClientId(), TestRegisteredClients.CLIENT_SECRET, ClientAuthenticationMethod.BASIC, null);
+				registeredClient.getClientId(), registeredClient.getClientSecret(), ClientAuthenticationMethod.BASIC, null);
 		OAuth2ClientAuthenticationToken authenticationResult =
 				(OAuth2ClientAuthenticationToken) this.authenticationProvider.authenticate(authentication);
+
+		verify(this.passwordEncoder).matches(any(), any());
 		assertThat(authenticationResult.isAuthenticated()).isTrue();
 		assertThat(authenticationResult.getPrincipal().toString()).isEqualTo(registeredClient.getClientId());
 		assertThat(authenticationResult.getCredentials()).isNull();