diff --git a/spring-web/src/main/java/org/springframework/http/client/MultipartBodyBuilder.java b/spring-web/src/main/java/org/springframework/http/client/MultipartBodyBuilder.java
index f9429225d9..1835f288e3 100644
--- a/spring-web/src/main/java/org/springframework/http/client/MultipartBodyBuilder.java
+++ b/spring-web/src/main/java/org/springframework/http/client/MultipartBodyBuilder.java
@@ -91,6 +91,12 @@ public final class MultipartBodyBuilder {
 				"publisher(String, Publisher, ParameterizedTypeReference) for adding Publisher parts");
 		}
 
+		if (part instanceof PublisherEntity<?,?>) {
+			PublisherPartBuilder<?, ?> builder = new PublisherPartBuilder<>((PublisherEntity<?, ?>) part);
+			this.parts.add(name, builder);
+			return builder;
+		}
+
 		Object partBody;
 		HttpHeaders partHeaders = new HttpHeaders();
 
@@ -154,7 +160,7 @@ public final class MultipartBodyBuilder {
 		Assert.notNull(elementType1, "'typeReference' must not be null");
 
 		HttpHeaders headers = new HttpHeaders();
-		PublisherPartBuilder<T, P> builder = new PublisherPartBuilder<>(publisher, typeReference, headers);
+		PublisherPartBuilder<T, P> builder = new PublisherPartBuilder<>(headers, publisher, typeReference);
 		this.parts.add(name, builder);
 		return builder;
 	}
@@ -239,11 +245,17 @@ public final class MultipartBodyBuilder {
 			this.resolvableType = ResolvableType.forClass(elementClass);
 		}
 
-		public PublisherPartBuilder(P body, ParameterizedTypeReference<S> typeReference, HttpHeaders headers) {
+		public PublisherPartBuilder(HttpHeaders headers, P body, ParameterizedTypeReference<S> typeReference) {
 			super(headers, body);
 			this.resolvableType = ResolvableType.forType(typeReference);
 		}
 
+		public PublisherPartBuilder(PublisherEntity<S, P> other) {
+			super(other.getHeaders(), other.getBody());
+			this.resolvableType = other.getResolvableType();
+		}
+
+
 		@Override
 		@SuppressWarnings("unchecked")
 		public HttpEntity<?> build() {
diff --git a/spring-web/src/test/java/org/springframework/http/client/MultipartBodyBuilderTests.java b/spring-web/src/test/java/org/springframework/http/client/MultipartBodyBuilderTests.java
index d948cd6fd2..e7f63a4365 100644
--- a/spring-web/src/test/java/org/springframework/http/client/MultipartBodyBuilderTests.java
+++ b/spring-web/src/test/java/org/springframework/http/client/MultipartBodyBuilderTests.java
@@ -26,6 +26,7 @@ import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.client.MultipartBodyBuilder.PublisherEntity;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
@@ -80,15 +81,36 @@ public class MultipartBodyBuilderTests {
 		assertNotNull(resultEntity);
 		assertEquals(publisher, resultEntity.getBody());
 		assertEquals(ResolvableType.forClass(String.class),
-				((MultipartBodyBuilder.PublisherEntity<?,?>) resultEntity).getResolvableType());
+				((PublisherEntity<?,?>) resultEntity).getResolvableType());
 		assertEquals("qux", resultEntity.getHeaders().getFirst("baz"));
 
 		resultEntity = result.getFirst("publisherPtr");
 		assertNotNull(resultEntity);
 		assertEquals(publisher, resultEntity.getBody());
 		assertEquals(ResolvableType.forClass(String.class),
-				((MultipartBodyBuilder.PublisherEntity<?,?>) resultEntity).getResolvableType());
+				((PublisherEntity<?,?>) resultEntity).getResolvableType());
 		assertEquals("qux", resultEntity.getHeaders().getFirst("baz"));
 	}
 
+	@Test // SPR-16601
+	public void publisherEntityAcceptedAsInput() {
+
+		Publisher<String> publisher = Flux.just("foo", "bar", "baz");
+		MultipartBodyBuilder builder = new MultipartBodyBuilder();
+		builder.asyncPart("publisherClass", publisher, String.class).header("baz", "qux");
+		HttpEntity<?> entity = builder.build().getFirst("publisherClass");
+
+		assertNotNull(entity);
+		assertEquals(PublisherEntity.class, entity.getClass());
+
+		// Now build a new MultipartBodyBuilder, as BodyInserters.fromMultipartData would do...
+
+		builder = new MultipartBodyBuilder();
+		builder.part("publisherClass", entity);
+		entity = builder.build().getFirst("publisherClass");
+
+		assertNotNull(entity);
+		assertEquals(PublisherEntity.class, entity.getClass());
+	}
+
 }
\ No newline at end of file