diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
index e2bbb004f93..f678b9d6f22 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
@@ -1522,9 +1522,12 @@ public class ApiClient {
         for (Entry<String, Object> param : formParams.entrySet()) {
             if (param.getValue() instanceof File) {
                 File file = (File) param.getValue();
-                Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"; filename=\"" + file.getName() + "\"");
-                MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
-                mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+                addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+            } else if (param.getValue() instanceof List) {
+                List<File> files = (List<File>) param.getValue();
+                for (File file : files) {
+                    addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+                }
             } else {
                 Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"");
                 mpBuilder.addPart(partHeaders, RequestBody.create(parameterToString(param.getValue()), null));
@@ -1548,6 +1551,19 @@ public class ApiClient {
         }
     }
 
+    /**
+     * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
+     *
+     * @param mpBuilder MultipartBody.Builder 
+     * @param key The key of the Header element
+     * @param file The file to add to the Header
+     */ 
+    private void addPartToMultiPartBuilder(MultipartBody.Builder mpBuilder, String key, File file) {
+        Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
+        MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
+        mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+    }
+
     /**
      * Get network interceptor to add it to the httpClient to track download progress for
      * async requests.
diff --git a/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
index 6c97a04c6b4..7b52fe547a9 100644
--- a/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
@@ -1317,9 +1317,12 @@ public class ApiClient {
         for (Entry<String, Object> param : formParams.entrySet()) {
             if (param.getValue() instanceof File) {
                 File file = (File) param.getValue();
-                Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"; filename=\"" + file.getName() + "\"");
-                MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
-                mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+                addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+            } else if (param.getValue() instanceof List) {
+                List<File> files = (List<File>) param.getValue();
+                for (File file : files) {
+                    addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+                }
             } else {
                 Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"");
                 mpBuilder.addPart(partHeaders, RequestBody.create(parameterToString(param.getValue()), null));
@@ -1343,6 +1346,19 @@ public class ApiClient {
         }
     }
 
+    /**
+     * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
+     *
+     * @param mpBuilder MultipartBody.Builder 
+     * @param key The key of the Header element
+     * @param file The file to add to the Header
+     */ 
+    private void addPartToMultiPartBuilder(MultipartBody.Builder mpBuilder, String key, File file) {
+        Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
+        MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
+        mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+    }
+
     /**
      * Get network interceptor to add it to the httpClient to track download progress for
      * async requests.
diff --git a/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
index eb4b02d4f32..bb5a40250e7 100644
--- a/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
@@ -1395,9 +1395,12 @@ public class ApiClient {
         for (Entry<String, Object> param : formParams.entrySet()) {
             if (param.getValue() instanceof File) {
                 File file = (File) param.getValue();
-                Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"; filename=\"" + file.getName() + "\"");
-                MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
-                mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+                addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+            } else if (param.getValue() instanceof List) {
+                List<File> files = (List<File>) param.getValue();
+                for (File file : files) {
+                    addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+                }
             } else {
                 Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"");
                 mpBuilder.addPart(partHeaders, RequestBody.create(parameterToString(param.getValue()), null));
@@ -1421,6 +1424,19 @@ public class ApiClient {
         }
     }
 
+    /**
+     * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
+     *
+     * @param mpBuilder MultipartBody.Builder 
+     * @param key The key of the Header element
+     * @param file The file to add to the Header
+     */ 
+    private void addPartToMultiPartBuilder(MultipartBody.Builder mpBuilder, String key, File file) {
+        Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
+        MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
+        mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+    }
+
     /**
      * Get network interceptor to add it to the httpClient to track download progress for
      * async requests.
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
index c3098921833..627f9ac88d5 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
@@ -1396,9 +1396,12 @@ public class ApiClient {
         for (Entry<String, Object> param : formParams.entrySet()) {
             if (param.getValue() instanceof File) {
                 File file = (File) param.getValue();
-                Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"; filename=\"" + file.getName() + "\"");
-                MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
-                mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+                addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+            } else if (param.getValue() instanceof List) {
+                List<File> files = (List<File>) param.getValue();
+                for (File file : files) {
+                    addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+                }
             } else {
                 Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"");
                 mpBuilder.addPart(partHeaders, RequestBody.create(parameterToString(param.getValue()), null));
@@ -1422,6 +1425,19 @@ public class ApiClient {
         }
     }
 
+    /**
+     * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
+     *
+     * @param mpBuilder MultipartBody.Builder 
+     * @param key The key of the Header element
+     * @param file The file to add to the Header
+     */ 
+    private void addPartToMultiPartBuilder(MultipartBody.Builder mpBuilder, String key, File file) {
+        Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
+        MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
+        mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+    }
+
     /**
      * Get network interceptor to add it to the httpClient to track download progress for
      * async requests.
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
index d745edd6e62..081e1c1f34c 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
@@ -1415,9 +1415,12 @@ public class ApiClient {
         for (Entry<String, Object> param : formParams.entrySet()) {
             if (param.getValue() instanceof File) {
                 File file = (File) param.getValue();
-                Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"; filename=\"" + file.getName() + "\"");
-                MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
-                mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+                addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+            } else if (param.getValue() instanceof List) {
+                List<File> files = (List<File>) param.getValue();
+                for (File file : files) {
+                    addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
+                }
             } else {
                 Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + param.getKey() + "\"");
                 mpBuilder.addPart(partHeaders, RequestBody.create(parameterToString(param.getValue()), null));
@@ -1441,6 +1444,19 @@ public class ApiClient {
         }
     }
 
+    /**
+     * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
+     *
+     * @param mpBuilder MultipartBody.Builder 
+     * @param key The key of the Header element
+     * @param file The file to add to the Header
+     */ 
+    private void addPartToMultiPartBuilder(MultipartBody.Builder mpBuilder, String key, File file) {
+        Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
+        MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
+        mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
+    }
+
     /**
      * Get network interceptor to add it to the httpClient to track download progress for
      * async requests.