diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
index 6265bea2bdf..1ac723a984e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
@@ -627,6 +627,13 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
                     }
                 }
 
+                // import okhttp3.MultipartBody if any parameter is a file
+                for (CodegenParameter param : operation.allParams) {
+                    if (Boolean.TRUE.equals(param.isFile)) {
+                        operations.put("x-kotlin-multipart-import", true);
+                    }
+                }
+
                 if (usesRetrofit2Library() && StringUtils.isNotEmpty(operation.path) && operation.path.startsWith("/")) {
                     operation.path = operation.path.substring(1);
                 }
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/api.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/api.mustache
index 99e6b204d0e..5bb18f913f1 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/api.mustache
@@ -41,6 +41,12 @@ import io.reactivex.rxjava3.core.Completable;
 {{/imports}}
 
 {{#operations}}
+{{#x-kotlin-multipart-import}}
+{{^isMultipart}}
+import okhttp3.MultipartBody
+
+{{/isMultipart}}
+{{/x-kotlin-multipart-import}}
 interface {{classname}} {
     {{#operation}}
     /**
@@ -76,4 +82,4 @@ interface {{classname}} {
 
     {{/operation}}
 }
-{{/operations}}
\ No newline at end of file
+{{/operations}}
diff --git a/pom.xml b/pom.xml
index 0b77ce578f6..d26e2db1ac1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1360,6 +1360,8 @@
                 <module>samples/client/petstore/erlang-proper</module>
                 <module>samples/client/petstore/kotlin-multiplatform</module>
                 <!--<module>samples/client/petstore/kotlin/</module>-->
+                <module>samples/client/petstore/kotlin-retrofit2</module>
+                <module>samples/client/petstore/kotlin-retrofit2-rx3</module>
                 <module>samples/client/petstore/kotlin-jackson/</module>
                 <module>samples/client/petstore/kotlin-gson/</module>
                 <module>samples/client/petstore/kotlin-nonpublic/</module>
diff --git a/samples/client/petstore/kotlin-retrofit2-rx3/pom.xml b/samples/client/petstore/kotlin-retrofit2-rx3/pom.xml
new file mode 100644
index 00000000000..1ee09680f37
--- /dev/null
+++ b/samples/client/petstore/kotlin-retrofit2-rx3/pom.xml
@@ -0,0 +1,46 @@
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.openapitools</groupId>
+    <artifactId>KotlinRetrofit2Rx3PetstoreClientTests</artifactId>
+    <packaging>pom</packaging>
+    <version>1.0-SNAPSHOT</version>
+    <name>Kotlin Retrofit2 Rx3 Petstore Client</name>
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2.1</version>
+                <executions>
+                    <execution>
+                        <id>bundle-test</id>
+                        <phase>integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>gradle</executable>
+                            <arguments>
+                                <argument>test</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>
diff --git a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/apis/PetApi.kt b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
index d33f1a00540..b52cebf4c31 100644
--- a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
+++ b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
@@ -9,6 +9,8 @@ import io.reactivex.rxjava3.core.Completable;
 import org.openapitools.client.models.ApiResponse
 import org.openapitools.client.models.Pet
 
+import okhttp3.MultipartBody
+
 interface PetApi {
     /**
      * Add a new pet to the store
diff --git a/samples/client/petstore/kotlin-retrofit2/pom.xml b/samples/client/petstore/kotlin-retrofit2/pom.xml
new file mode 100644
index 00000000000..a2a34c203fa
--- /dev/null
+++ b/samples/client/petstore/kotlin-retrofit2/pom.xml
@@ -0,0 +1,46 @@
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.openapitools</groupId>
+    <artifactId>KotlinRetrofit2PetstoreClientTests</artifactId>
+    <packaging>pom</packaging>
+    <version>1.0-SNAPSHOT</version>
+    <name>Kotlin Retrofit2 Petstore Client</name>
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2.1</version>
+                <executions>
+                    <execution>
+                        <id>bundle-test</id>
+                        <phase>integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>gradle</executable>
+                            <arguments>
+                                <argument>test</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>
diff --git a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/apis/PetApi.kt b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
index f3f9c057d24..4d78248129c 100644
--- a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
+++ b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/apis/PetApi.kt
@@ -8,6 +8,8 @@ import okhttp3.RequestBody
 import org.openapitools.client.models.ApiResponse
 import org.openapitools.client.models.Pet
 
+import okhttp3.MultipartBody
+
 interface PetApi {
     /**
      * Add a new pet to the store