diff --git a/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapper.java b/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapper.java
index 63ea201ac..036159d15 100644
--- a/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapper.java
+++ b/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapper.java
@@ -24,6 +24,7 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jetbrains.annotations.NotNull;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -158,7 +159,16 @@ public class TraceFunctionAroundWrapper extends FunctionAroundWrapper
 		if (targetFunction.isConsumer()) {
 			return targetFunction.apply(reactorStreamConsumer(mono));
 		}
-		final Mono<Message> function = ((Mono<Message>) targetFunction.apply(mono));
+		final Publisher<Message> function = ((Publisher<Message>) targetFunction.apply(mono));
+		if (function instanceof Mono) {
+			return messageMono(targetFunction, (Mono<Message>) function);
+		}
+		return messageFlux(targetFunction, (Flux<Message>) function);
+	}
+
+	@NotNull
+	private Mono<Message> messageMono(SimpleFunctionRegistry.FunctionInvocationWrapper targetFunction,
+			Mono<Message> function) {
 		return Mono.deferContextual(contextView -> {
 			MessageAndSpansAndScope msg = contextView.get(MessageAndSpansAndScope.class);
 			return function.doOnNext(message -> {
@@ -201,7 +211,16 @@ public class TraceFunctionAroundWrapper extends FunctionAroundWrapper
 		if (targetFunction.isConsumer()) {
 			return targetFunction.apply(reactorStreamConsumer(flux));
 		}
-		final Flux<Message> function = ((Flux<Message>) targetFunction.apply(flux));
+		final Publisher<Message> function = ((Publisher<Message>) targetFunction.apply(flux));
+		if (function instanceof Mono) {
+			return messageMono(targetFunction, (Mono<Message>) function);
+		}
+		return messageFlux(targetFunction, (Flux<Message>) function);
+	}
+
+	@NotNull
+	private Flux<Message> messageFlux(SimpleFunctionRegistry.FunctionInvocationWrapper targetFunction,
+			Flux<Message> function) {
 		return Flux.deferContextual(contextView -> {
 			MessageAndSpansAndScope msg = contextView.get(MessageAndSpansAndScope.class);
 			return function.doOnNext(message -> {
diff --git a/spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapperTests.java b/spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapperTests.java
index 6fd6ad2fd..3c8a0f17c 100644
--- a/spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapperTests.java
+++ b/spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapperTests.java
@@ -201,6 +201,25 @@ class TraceFunctionAroundWrapperTests {
 		assertThatAllSpansAreStartedAndStopped();
 	}
 
+	@Test
+	void should_trace_when_reactive_mono_to_flux_function() {
+		FunctionRegistration<ReactiveMonoToFluxFunction> registration = new FunctionRegistration<>(
+				new ReactiveMonoToFluxFunction(), "greeter").type(FunctionType.of(ReactiveMonoToFluxFunction.class));
+		catalog.register(registration);
+		FunctionInvocationWrapper function = catalog.lookup("greeter");
+
+		Message result = ((Flux<Message>) wrapper.apply(
+				Mono.just(MessageBuilder.withPayload("hello").setHeader("superHeader", "someValue").build()), function))
+						.blockFirst(Duration.ofSeconds(5));
+
+		assertThat(result.getPayload()).isEqualTo("HELLO");
+		assertThat(tracer.spans).hasSize(3);
+		assertThat(tracer.spans.get(0).name).isEqualTo("handle");
+		assertThat(tracer.spans.get(1).name).isEqualTo("greeter");
+		assertThat(tracer.spans.get(2).name).isEqualTo("send");
+		assertThatAllSpansAreStartedAndStopped();
+	}
+
 	@Test
 	void should_trace_when_reactive_flux_supplier() {
 		FunctionRegistration<ReactiveFluxGreeter> registration = new FunctionRegistration<>(new ReactiveFluxGreeter(),
@@ -234,6 +253,23 @@ class TraceFunctionAroundWrapperTests {
 		assertThatAllSpansAreStartedAndStopped();
 	}
 
+	@Test
+	void should_trace_when_reactive_flux_function_returns_mono() {
+		FunctionRegistration<ReactiveFluxToMonoFunction> registration = new FunctionRegistration<>(
+				new ReactiveFluxToMonoFunction(), "greeter").type(FunctionType.of(ReactiveFluxToMonoFunction.class));
+		catalog.register(registration);
+		FunctionInvocationWrapper function = catalog.lookup("greeter");
+
+		((Mono<Void>) wrapper.apply(
+				Flux.just(MessageBuilder.withPayload("hello").setHeader("superHeader", "someValue").build()), function))
+						.block(Duration.ofSeconds(5));
+
+		assertThat(tracer.spans).hasSize(2);
+		assertThat(tracer.spans.get(0).name).isEqualTo("handle");
+		assertThat(tracer.spans.get(1).name).isEqualTo("greeter");
+		assertThatAllSpansAreStartedAndStopped();
+	}
+
 	@Test
 	void should_trace_when_reactive_flux_consumer() {
 		ReactiveFluxGreeterConsumer consumer = new ReactiveFluxGreeterConsumer(this.tracer);
@@ -352,6 +388,16 @@ class TraceFunctionAroundWrapperTests {
 
 	}
 
+	private static class ReactiveMonoToFluxFunction implements Function<Mono<Message<String>>, Flux<Message<String>>> {
+
+		@Override
+		public Flux<Message<String>> apply(Mono<Message<String>> in) {
+			return Flux
+					.from(in.map(s -> MessageBuilder.fromMessage(s).withPayload(s.getPayload().toUpperCase()).build()));
+		}
+
+	}
+
 	private static class ReactiveFluxGreeter implements Supplier<Flux<Message<String>>> {
 
 		@Override
@@ -370,6 +416,16 @@ class TraceFunctionAroundWrapperTests {
 
 	}
 
+	private static class ReactiveFluxToMonoFunction implements Function<Flux<Message<String>>, Mono<Void>> {
+
+		@Override
+		public Mono<Void> apply(Flux<Message<String>> in) {
+			return in.map(s -> MessageBuilder.fromMessage(s).withPayload(s.getPayload().toUpperCase()).build())
+					.then(Mono.empty());
+		}
+
+	}
+
 	private static class ReactiveFluxGreeterConsumer implements Consumer<Flux<Message<String>>> {
 
 		String result;