diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java
index 015afbbd172..7d177667010 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java
@@ -275,12 +275,11 @@ public abstract class AbstractMessageConverterMethodProcessor extends AbstractMe
 						"No converter found for return value of type: " + valueType);
 			}
 
-			List<MediaType> compatibleMediaTypes = new ArrayList<>();
-			determineCompatibleMediaTypes(acceptableTypes, producibleTypes, compatibleMediaTypes);
+			List<MediaType> compatibleMediaTypes = determineCompatibleMediaTypes(acceptableTypes, producibleTypes);
 
 			// For ProblemDetail, fall back on RFC 9457 format
 			if (compatibleMediaTypes.isEmpty() && ProblemDetail.class.isAssignableFrom(valueType)) {
-				determineCompatibleMediaTypes(this.problemMediaTypes, producibleTypes, compatibleMediaTypes);
+				compatibleMediaTypes = determineCompatibleMediaTypes(this.problemMediaTypes, producibleTypes);
 			}
 
 			if (compatibleMediaTypes.isEmpty()) {
@@ -453,16 +452,18 @@ public abstract class AbstractMessageConverterMethodProcessor extends AbstractMe
 		return this.contentNegotiationManager.resolveMediaTypes(new ServletWebRequest(request));
 	}
 
-	private void determineCompatibleMediaTypes(
-			List<MediaType> acceptableTypes, List<MediaType> producibleTypes, List<MediaType> mediaTypesToUse) {
+	private List<MediaType> determineCompatibleMediaTypes(
+			List<MediaType> acceptableTypes, List<MediaType> producibleTypes) {
 
+		Set<MediaType> compatibleTypes = new LinkedHashSet<>();
 		for (MediaType requestedType : acceptableTypes) {
 			for (MediaType producibleType : producibleTypes) {
 				if (requestedType.isCompatibleWith(producibleType)) {
-					mediaTypesToUse.add(getMostSpecificMediaType(requestedType, producibleType));
+					compatibleTypes.add(getMostSpecificMediaType(requestedType, producibleType));
 				}
 			}
 		}
+		return new ArrayList<>(compatibleTypes);
 	}
 
 	/**
diff --git a/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessorTests.java b/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessorTests.java
index 00f40185196..d670167c3a7 100644
--- a/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessorTests.java
+++ b/spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessorTests.java
@@ -24,6 +24,8 @@ import java.lang.reflect.Type;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import com.fasterxml.jackson.annotation.JsonTypeName;
@@ -783,6 +785,24 @@ class RequestResponseBodyMethodProcessorTests {
 		assertThat(value).isEqualTo("foo");
 	}
 
+	@Test // gh-36300
+	void shouldNotDuplicateInCompatibleMediaTypes() throws Exception {
+		Method method = TestRestController.class.getMethod("handle");
+		MethodParameter returnType = new MethodParameter(method, -1);
+
+		List<HttpMessageConverter<?>> converters = List.of(new StringHttpMessageConverter(), new MappingJackson2HttpMessageConverter());
+		RequestResponseBodyMethodProcessor processor = new RequestResponseBodyMethodProcessor(converters);
+
+		String accept = Stream.iterate(1, i -> i + 1)
+				.limit(48).map(i -> "application/" + i)
+				.collect(Collectors.joining(","));
+		accept = accept + ", application/json";
+		this.servletRequest.addHeader("Accept", accept);
+
+		processor.writeWithMessageConverters("spring framework", returnType, this.request);
+	}
+
+
 	private void assertContentDisposition(RequestResponseBodyMethodProcessor processor,
 			boolean expectContentDisposition, String requestURI, String comment) throws Exception {