diff --git a/spring-web/src/main/java/org/springframework/http/ETag.java b/spring-web/src/main/java/org/springframework/http/ETag.java
index be2ded98918..0acfaefc048 100644
--- a/spring-web/src/main/java/org/springframework/http/ETag.java
+++ b/spring-web/src/main/java/org/springframework/http/ETag.java
@@ -134,16 +134,27 @@ public record ETag(String tag, boolean weak) {
 		return result;
 	}
 
-	public static String format(String etag) {
-		if (!etag.startsWith("\"") && !etag.startsWith("W/\"")) {
-			etag = "\"" + etag;
+	/**
+	 * Add quotes around the ETag value if not present already.
+	 * @param tag the ETag value
+	 * @return the resulting, quoted value
+	 * @since 6.2
+	 */
+	public static String quoteETagIfNecessary(String tag) {
+		if (tag.startsWith("W/\"")) {
+			if (tag.length() > 3 && tag.endsWith("\"")) {
+				return tag;
+			}
 		}
-		if (!etag.endsWith("\"")) {
-			etag = etag + "\"";
+		else if (tag.startsWith("\"")) {
+			if (tag.length() > 1 && tag.endsWith("\"")) {
+				return tag;
+			}
 		}
-		return etag;
+		return ("\"" + tag + "\"");
 	}
 
+
 	private enum State {
 
 		BEFORE_QUOTES, IN_QUOTES, AFTER_QUOTES
diff --git a/spring-web/src/main/java/org/springframework/http/ResponseEntity.java b/spring-web/src/main/java/org/springframework/http/ResponseEntity.java
index 8ab005e2935..ea62bc565a2 100644
--- a/spring-web/src/main/java/org/springframework/http/ResponseEntity.java
+++ b/spring-web/src/main/java/org/springframework/http/ResponseEntity.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -568,11 +568,9 @@ public class ResponseEntity<T> extends HttpEntity<T> {
 		}
 
 		@Override
-		public BodyBuilder eTag(@Nullable String etag) {
-			if (etag != null) {
-				etag = ETag.format(etag);
-			}
-			this.headers.setETag(etag);
+		public BodyBuilder eTag(@Nullable String eTag) {
+			eTag = (eTag != null ? ETag.quoteETagIfNecessary(eTag) : eTag);
+			this.headers.setETag(eTag);
 			return this;
 		}
 
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilder.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilder.java
index 7722c53eb13..75c01260858 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilder.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -28,10 +28,17 @@ import java.util.Optional;
 import java.util.Set;
 import java.util.function.Consumer;
 
-import org.springframework.http.*;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.codec.Hints;
+import org.springframework.http.CacheControl;
+import org.springframework.http.ETag;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseCookie;
 import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
@@ -141,9 +148,9 @@ class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T> {
 	}
 
 	@Override
-	public EntityResponse.Builder<T> eTag(String etag) {
-		etag = ETag.format(etag);
-		this.headers.setETag(etag);
+	public EntityResponse.Builder<T> eTag(String eTag) {
+		eTag = ETag.quoteETagIfNecessary(eTag);
+		this.headers.setETag(eTag);
 		return this;
 	}
 
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java
index 7c6e2ee9901..00443c9d48b 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java
@@ -32,11 +32,18 @@ import java.util.function.Consumer;
 import java.util.function.Function;
 
 import org.reactivestreams.Publisher;
-import org.springframework.http.*;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.codec.Hints;
+import org.springframework.http.CacheControl;
+import org.springframework.http.ETag;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
+import org.springframework.http.ReactiveHttpOutputMessage;
+import org.springframework.http.ResponseCookie;
 import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
@@ -140,10 +147,10 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 	}
 
 	@Override
-	public ServerResponse.BodyBuilder eTag(String etag) {
-		Assert.notNull(etag, "etag must not be null");
-		etag = ETag.format(etag);
-		this.headers.setETag(etag);
+	public ServerResponse.BodyBuilder eTag(String eTag) {
+		Assert.notNull(eTag, "etag must not be null");
+		eTag = ETag.quoteETagIfNecessary(eTag);
+		this.headers.setETag(eTag);
 		return this;
 	}
 
diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultEntityResponseBuilder.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultEntityResponseBuilder.java
index e44cd3131ae..bed228e2644 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultEntityResponseBuilder.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultEntityResponseBuilder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -45,7 +45,15 @@ import org.springframework.core.ResolvableType;
 import org.springframework.core.io.InputStreamResource;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.ResourceRegion;
-import org.springframework.http.*;
+import org.springframework.http.CacheControl;
+import org.springframework.http.ETag;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpRange;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.InvalidMediaTypeException;
+import org.springframework.http.MediaType;
 import org.springframework.http.converter.GenericHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.SmartHttpMessageConverter;
@@ -158,9 +166,9 @@ final class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T>
 	}
 
 	@Override
-	public EntityResponse.Builder<T> eTag(String etag) {
-		etag = ETag.format(etag);
-		this.headers.setETag(etag);
+	public EntityResponse.Builder<T> eTag(String eTag) {
+		eTag = ETag.quoteETagIfNecessary(eTag);
+		this.headers.setETag(eTag);
 		return this;
 	}
 
diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultServerResponseBuilder.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultServerResponseBuilder.java
index d5611d19c5f..46ea10a80f7 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultServerResponseBuilder.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultServerResponseBuilder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -30,7 +30,12 @@ import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 
 import org.springframework.core.ParameterizedTypeReference;
-import org.springframework.http.*;
+import org.springframework.http.CacheControl;
+import org.springframework.http.ETag;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
@@ -122,10 +127,10 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 	}
 
 	@Override
-	public ServerResponse.BodyBuilder eTag(String etag) {
-		Assert.notNull(etag, "etag must not be null");
-		etag = ETag.format(etag);
-		this.headers.setETag(etag);
+	public ServerResponse.BodyBuilder eTag(String eTag) {
+		Assert.notNull(eTag, "etag must not be null");
+		eTag = ETag.quoteETagIfNecessary(eTag);
+		this.headers.setETag(eTag);
 		return this;
 	}