diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfiguration.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfiguration.java
index 4649192258..05f6eaadcf 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfiguration.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfiguration.java
@@ -55,6 +55,7 @@ import org.springframework.graphql.server.webflux.SchemaHandler;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.reactive.HandlerMapping;
@@ -112,6 +113,7 @@ public class GraphQlWebFluxAutoConfiguration {
 		RouterFunctions.Builder builder = RouterFunctions.route();
 		builder.route(GraphQlRequestPredicates.graphQlHttp(path), httpHandler::handleRequest);
 		builder.route(GraphQlRequestPredicates.graphQlSse(path), sseHandler::handleRequest);
+		builder.POST(path, this::unsupportedMediaType);
 		builder.GET(path, this::onlyAllowPost);
 		if (properties.getGraphiql().isEnabled()) {
 			GraphiQlHandler graphQlHandler = new GraphiQlHandler(path, properties.getWebsocket().getPath());
@@ -124,6 +126,14 @@ public class GraphQlWebFluxAutoConfiguration {
 		return builder.build();
 	}
 
+	private Mono<ServerResponse> unsupportedMediaType(ServerRequest request) {
+		return ServerResponse.status(HttpStatus.UNSUPPORTED_MEDIA_TYPE).headers(this::acceptJson).build();
+	}
+
+	private void acceptJson(HttpHeaders headers) {
+		headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
+	}
+
 	private Mono<ServerResponse> onlyAllowPost(ServerRequest request) {
 		return ServerResponse.status(HttpStatus.METHOD_NOT_ALLOWED).headers(this::onlyAllowPost).build();
 	}
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java
index 0c44464042..c36823761e 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java
@@ -117,6 +117,7 @@ public class GraphQlWebMvcAutoConfiguration {
 		RouterFunctions.Builder builder = RouterFunctions.route();
 		builder.route(GraphQlRequestPredicates.graphQlHttp(path), httpHandler::handleRequest);
 		builder.route(GraphQlRequestPredicates.graphQlSse(path), sseHandler::handleRequest);
+		builder.POST(path, this::unsupportedMediaType);
 		builder.GET(path, this::onlyAllowPost);
 		if (properties.getGraphiql().isEnabled()) {
 			GraphiQlHandler graphiQLHandler = new GraphiQlHandler(path, properties.getWebsocket().getPath());
@@ -129,6 +130,14 @@ public class GraphQlWebMvcAutoConfiguration {
 		return builder.build();
 	}
 
+	private ServerResponse unsupportedMediaType(ServerRequest request) {
+		return ServerResponse.status(HttpStatus.UNSUPPORTED_MEDIA_TYPE).headers(this::acceptJson).build();
+	}
+
+	private void acceptJson(HttpHeaders headers) {
+		headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
+	}
+
 	private ServerResponse onlyAllowPost(ServerRequest request) {
 		return ServerResponse.status(HttpStatus.METHOD_NOT_ALLOWED).headers(this::onlyAllowPost).build();
 	}
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfigurationTests.java
index bf4dc6695d..51978cc79f 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfigurationTests.java
@@ -119,7 +119,23 @@ class GraphQlWebFluxAutoConfigurationTests {
 	}
 
 	@Test
-	void httpGetQueryShouldBeSupported() {
+	void unsupportedContentTypeShouldBeRejected() {
+		testWithWebClient((client) -> {
+			String query = "{ bookById(id: \\\"book-1\\\"){ id name pageCount author } }";
+			client.post()
+				.uri("/graphql")
+				.contentType(MediaType.TEXT_PLAIN)
+				.bodyValue("{  \"query\": \"" + query + "\"}")
+				.exchange()
+				.expectStatus()
+				.isEqualTo(HttpStatus.UNSUPPORTED_MEDIA_TYPE)
+				.expectHeader()
+				.valueEquals("Accept", "application/json");
+		});
+	}
+
+	@Test
+	void httpGetQueryShouldBeRejected() {
 		testWithWebClient((client) -> {
 			String query = "{ bookById(id: \\\"book-1\\\"){ id name pageCount author } }";
 			client.get()
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java
index 260f122c14..9f6a455ab0 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java
@@ -111,7 +111,20 @@ class GraphQlWebMvcAutoConfigurationTests {
 	}
 
 	@Test
-	void httpGetQueryShouldBeSupported() {
+	void unsupportedContentTypeShouldBeRejected() {
+		withMockMvc((mvc) -> {
+			String query = "{ bookById(id: \\\"book-1\\\"){ id name pageCount author } }";
+			assertThat(mvc.post()
+				.uri("/graphql")
+				.content("{\"query\": \"" + query + "\"}")
+				.contentType(MediaType.TEXT_PLAIN)).hasStatus(HttpStatus.UNSUPPORTED_MEDIA_TYPE)
+				.headers()
+				.hasValue("Accept", "application/json");
+		});
+	}
+
+	@Test
+	void httpGetQueryShouldBeRejected() {
 		withMockMvc((mvc) -> {
 			String query = "{ bookById(id: \\\"book-1\\\"){ id name pageCount author } }";
 			assertThat(mvc.get().uri("/graphql?query={query}", "{\"query\": \"" + query + "\"}"))