diff --git a/spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageReader.java b/spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageReader.java
index a16063d1b5..ee9f4ffc9a 100644
--- a/spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageReader.java
+++ b/spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageReader.java
@@ -31,6 +31,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.Decoder;
+import org.springframework.core.codec.StringDecoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DataBufferUtils;
@@ -57,6 +58,8 @@ public class ServerSentEventHttpMessageReader implements HttpMessageReader<Objec
 
 	private static final DataBufferFactory bufferFactory = new DefaultDataBufferFactory();
 
+	private static final StringDecoder stringDecoder = new StringDecoder(false);
+
 
 	private final List<Decoder<?>> dataDecoders;
 
@@ -178,6 +181,13 @@ public class ServerSentEventHttpMessageReader implements HttpMessageReader<Objec
 	public Mono<Object> readMono(ResolvableType elementType, ReactiveHttpInputMessage inputMessage,
 			Map<String, Object> hints) {
 
+		// Let's give StringDecoder a chance since SSE is ordered ahead of it
+
+		if (String.class.equals(elementType.getRawClass())) {
+			Flux<DataBuffer> body = inputMessage.getBody();
+			return stringDecoder.decodeToMono(body, elementType, null, null).cast(Object.class);
+		}
+
 		return Mono.error(new UnsupportedOperationException(
 				"ServerSentEventHttpMessageReader only supports reading stream of events as a Flux"));
 	}
diff --git a/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageReaderTests.java b/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageReaderTests.java
index dd725b4252..56dd5a1eea 100644
--- a/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageReaderTests.java
+++ b/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageReaderTests.java
@@ -21,6 +21,7 @@ import java.util.Collections;
 
 import org.junit.Test;
 import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
 import org.springframework.core.ResolvableType;
@@ -157,4 +158,18 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractDataBufferAll
 				.verify();
 	}
 
+	@Test // SPR-15331
+	public void decodeFullContentAsString() {
+
+		String body = "data:foo\ndata:bar\n\ndata:baz\n\n";
+		MockServerHttpRequest request = MockServerHttpRequest.post("/").body(body);
+
+		String actual = messageReader
+				.readMono(ResolvableType.forClass(String.class), request, Collections.emptyMap())
+				.cast(String.class)
+				.block(Duration.ZERO);
+
+		assertEquals(body, actual);
+	}
+
 }