diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
index 66e77122a811..ea19748fbfbc 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
@@ -25,6 +25,7 @@ import okhttp3.Interceptor
 import okhttp3.OkHttpClient
 import retrofit2.Retrofit
 import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Converter
 import retrofit2.converter.scalars.ScalarsConverterFactory
 {{#useRxJava}}
 import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory
@@ -55,7 +56,8 @@ import okhttp3.MediaType.Companion.toMediaType
     private var baseUrl: String = defaultBasePath,
     private val okHttpClientBuilder: OkHttpClient.Builder? = null{{^kotlinx_serialization}},
     private val serializerBuilder: {{#gson}}Gson{{/gson}}{{#moshi}}Moshi.{{/moshi}}Builder = Serializer.{{#gson}}gson{{/gson}}{{#moshi}}moshi{{/moshi}}Builder{{/kotlinx_serialization}},
-    private val okHttpClient : OkHttpClient? = null
+    private val okHttpClient : OkHttpClient? = null,
+    private val converterFactory: Converter.Factory? = null,
 ) {
     private val apiAuthorizations = mutableMapOf<String, Interceptor>()
     var logger: ((String) -> Unit)? = null
@@ -81,6 +83,11 @@ import okhttp3.MediaType.Companion.toMediaType
             {{#kotlinx_serialization}}
             .addConverterFactory(jvmJson.asConverterFactory("application/json".toMediaType()))
             {{/kotlinx_serialization}}
+            .apply {
+                if (converterFactory != null) {
+                    addConverterFactory(converterFactory)
+                }
+            }
     }
 
     private val clientBuilder: OkHttpClient.Builder by lazy {
diff --git a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b721ee141b04..a5aaa332be80 100644
--- a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -11,6 +11,7 @@ import okhttp3.Interceptor
 import okhttp3.OkHttpClient
 import retrofit2.Retrofit
 import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Converter
 import retrofit2.converter.scalars.ScalarsConverterFactory
 
 import com.jakewharton.retrofit2.converter.kotlinx.serialization.asConverterFactory
@@ -20,7 +21,8 @@ import okhttp3.MediaType.Companion.toMediaType
 class ApiClient(
     private var baseUrl: String = defaultBasePath,
     private val okHttpClientBuilder: OkHttpClient.Builder? = null,
-    private val okHttpClient : OkHttpClient? = null
+    private val okHttpClient : OkHttpClient? = null,
+    private val converterFactory: Converter.Factory? = null,
 ) {
     private val apiAuthorizations = mutableMapOf<String, Interceptor>()
     var logger: ((String) -> Unit)? = null
@@ -30,6 +32,11 @@ class ApiClient(
             .baseUrl(baseUrl)
             .addConverterFactory(ScalarsConverterFactory.create())
             .addConverterFactory(jvmJson.asConverterFactory("application/json".toMediaType()))
+            .apply {
+                if (converterFactory != null) {
+                    addConverterFactory(converterFactory)
+                }
+            }
     }
 
     private val clientBuilder: OkHttpClient.Builder by lazy {
diff --git a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 1b1edd60ae21..cc63b570177a 100644
--- a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -11,6 +11,7 @@ import okhttp3.Interceptor
 import okhttp3.OkHttpClient
 import retrofit2.Retrofit
 import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Converter
 import retrofit2.converter.scalars.ScalarsConverterFactory
 import retrofit2.adapter.rxjava3.RxJava3CallAdapterFactory
 import com.squareup.moshi.Moshi
@@ -21,7 +22,8 @@ class ApiClient(
     private var baseUrl: String = defaultBasePath,
     private val okHttpClientBuilder: OkHttpClient.Builder? = null,
     private val serializerBuilder: Moshi.Builder = Serializer.moshiBuilder,
-    private val okHttpClient : OkHttpClient? = null
+    private val okHttpClient : OkHttpClient? = null,
+    private val converterFactory: Converter.Factory? = null,
 ) {
     private val apiAuthorizations = mutableMapOf<String, Interceptor>()
     var logger: ((String) -> Unit)? = null
@@ -33,6 +35,11 @@ class ApiClient(
 
             .addCallAdapterFactory(RxJava3CallAdapterFactory.create())
             .addConverterFactory(MoshiConverterFactory.create(serializerBuilder.build()))
+            .apply {
+                if (converterFactory != null) {
+                    addConverterFactory(converterFactory)
+                }
+            }
     }
 
     private val clientBuilder: OkHttpClient.Builder by lazy {
diff --git a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 667359c1f227..bee954129e6b 100644
--- a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -11,6 +11,7 @@ import okhttp3.Interceptor
 import okhttp3.OkHttpClient
 import retrofit2.Retrofit
 import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Converter
 import retrofit2.converter.scalars.ScalarsConverterFactory
 import com.squareup.moshi.Moshi
 import retrofit2.converter.moshi.MoshiConverterFactory
@@ -20,7 +21,8 @@ class ApiClient(
     private var baseUrl: String = defaultBasePath,
     private val okHttpClientBuilder: OkHttpClient.Builder? = null,
     private val serializerBuilder: Moshi.Builder = Serializer.moshiBuilder,
-    private val okHttpClient : OkHttpClient? = null
+    private val okHttpClient : OkHttpClient? = null,
+    private val converterFactory: Converter.Factory? = null,
 ) {
     private val apiAuthorizations = mutableMapOf<String, Interceptor>()
     var logger: ((String) -> Unit)? = null
@@ -30,6 +32,11 @@ class ApiClient(
             .baseUrl(baseUrl)
             .addConverterFactory(ScalarsConverterFactory.create())
             .addConverterFactory(MoshiConverterFactory.create(serializerBuilder.build()))
+            .apply {
+                if (converterFactory != null) {
+                    addConverterFactory(converterFactory)
+                }
+            }
     }
 
     private val clientBuilder: OkHttpClient.Builder by lazy {