diff --git a/spring-boot-project/spring-boot-docker-compose/src/main/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactory.java b/spring-boot-project/spring-boot-docker-compose/src/main/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactory.java
index 0684428468..34e748c143 100644
--- a/spring-boot-project/spring-boot-docker-compose/src/main/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactory.java
+++ b/spring-boot-project/spring-boot-docker-compose/src/main/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactory.java
@@ -30,6 +30,7 @@ import org.springframework.boot.docker.compose.service.connection.DockerComposeC
  * @author Moritz Halbritter
  * @author Andy Wilkinson
  * @author Phillip Webb
+ * @author Scott Frederick
  */
 class MongoDockerComposeConnectionDetailsFactory extends DockerComposeConnectionDetailsFactory<MongoConnectionDetails> {
 
@@ -73,6 +74,9 @@ class MongoDockerComposeConnectionDetailsFactory extends DockerComposeConnection
 			builder.append(service.ports().get(MONGODB_PORT));
 			builder.append("/");
 			builder.append((environment.getDatabase() != null) ? environment.getDatabase() : "test");
+			if (environment.getUsername() != null) {
+				builder.append("?authSource=admin");
+			}
 			return new ConnectionString(builder.toString());
 		}
 
diff --git a/spring-boot-project/spring-boot-docker-compose/src/test/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactoryIntegrationTests.java b/spring-boot-project/spring-boot-docker-compose/src/test/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactoryIntegrationTests.java
index f4ff8fdfbe..01777d1a74 100644
--- a/spring-boot-project/spring-boot-docker-compose/src/test/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactoryIntegrationTests.java
+++ b/spring-boot-project/spring-boot-docker-compose/src/test/java/org/springframework/boot/docker/compose/service/connection/mongo/MongoDockerComposeConnectionDetailsFactoryIntegrationTests.java
@@ -16,6 +16,7 @@
 
 package org.springframework.boot.docker.compose.service.connection.mongo;
 
+import com.mongodb.ConnectionString;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.autoconfigure.mongo.MongoConnectionDetails;
@@ -29,6 +30,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Moritz Halbritter
  * @author Andy Wilkinson
  * @author Phillip Webb
+ * @author Scott Frederick
  */
 class MongoDockerComposeConnectionDetailsFactoryIntegrationTests extends AbstractDockerComposeIntegrationTests {
 
@@ -39,8 +41,11 @@ class MongoDockerComposeConnectionDetailsFactoryIntegrationTests extends Abstrac
 	@Test
 	void runCreatesConnectionDetails() {
 		MongoConnectionDetails connectionDetails = run(MongoConnectionDetails.class);
-		assertThat(connectionDetails.getConnectionString().toString()).startsWith("mongodb://root:secret@")
-			.endsWith("/mydatabase");
+		ConnectionString connectionString = connectionDetails.getConnectionString();
+		assertThat(connectionString.getCredential().getUserName()).isEqualTo("root");
+		assertThat(connectionString.getCredential().getPassword()).isEqualTo("secret".toCharArray());
+		assertThat(connectionString.getCredential().getSource()).isEqualTo("admin");
+		assertThat(connectionString.getDatabase()).isEqualTo("mydatabase");
 		assertThat(connectionDetails.getGridFs()).isNull();
 	}