diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index 1c995009e018..015bfb9ac1bd 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -67,7 +67,23 @@ class {{{classname}}} {
         {{^required}}
     if ({{{paramName}}} != null) {
           {{/required}}
+        {{#isMap}}
+          {{#isExplode}}
+            {{^isDeepObject}}
+      // form style, explode: one query parameter per entry, keyed by the property name; a collection repeats the key per non-null element
+      {{#isFreeFormObject}}({{{paramName}}} as Map){{/isFreeFormObject}}{{^isFreeFormObject}}{{{paramName}}}{{/isFreeFormObject}}.forEach((entryKey, dynamic entryValue) => queryParams.addAll(_queryParams('multi', entryKey.toString(), entryValue is Iterable ? entryValue.where((e) => e != null).toList() : entryValue)));
+            {{/isDeepObject}}
+            {{#isDeepObject}}
       queryParams.addAll(_queryParams('{{{collectionFormat}}}', '{{{baseName}}}', {{{paramName}}}));
+            {{/isDeepObject}}
+          {{/isExplode}}
+          {{^isExplode}}
+      queryParams.addAll(_queryParams('{{{collectionFormat}}}', '{{{baseName}}}', {{{paramName}}}));
+          {{/isExplode}}
+        {{/isMap}}
+        {{^isMap}}
+      queryParams.addAll(_queryParams('{{{collectionFormat}}}', '{{{baseName}}}', {{{paramName}}}));
+        {{/isMap}}
           {{^required}}
     }
         {{/required}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/dart/DartClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/dart/DartClientCodegenTest.java
index 2215908d3d65..301193c8fa63 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/dart/DartClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/dart/DartClientCodegenTest.java
@@ -137,6 +137,34 @@ public void testObjectArrayDoesNotUseListFromJson() throws Exception {
         TestUtils.assertFileContains(modelFile.toPath(), "cast<Object>");
     }
 
+    @Test(description = "Verify a form style, exploded map query parameter goes on the wire one entry per parameter")
+    public void testExplodedObjectQueryParameter() throws Exception {
+        List<File> files = generateDartNativeFromSpec(
+                "src/test/resources/3_0/exploded-object-query-param.yaml");
+
+        File apiFile = files.stream()
+                .filter(f -> f.getName().equals("default_api.dart"))
+                .findFirst()
+                .orElseThrow(() -> new AssertionError("default_api.dart not found in generated files"));
+
+        // form style with explode - the default - puts every entry on the wire under its own
+        // property name. Handing the whole map to _queryParams stringifies it with
+        // Map.toString(), which is what used to happen. A collection value repeats the key per
+        // non-null element ('multi').
+        TestUtils.assertFileContains(apiFile.toPath(),
+                "(filter as Map).forEach((entryKey, dynamic entryValue) => queryParams.addAll(_queryParams('multi', entryKey.toString(), entryValue is Iterable ? entryValue.where((e) => e != null).toList() : entryValue)));");
+        TestUtils.assertFileNotContains(apiFile.toPath(), "_queryParams('', 'filter', filter)");
+
+        // a declared map behaves the same way, and needs no cast
+        TestUtils.assertFileContains(apiFile.toPath(),
+                "typedFilter.forEach((entryKey, dynamic entryValue) => queryParams.addAll(_queryParams('multi', entryKey.toString(), entryValue is Iterable ? entryValue.where((e) => e != null).toList() : entryValue)));");
+
+        // deepObject and form without explode both keep a single parameter
+        TestUtils.assertFileContains(apiFile.toPath(),
+                "_queryParams('', 'deepFilter', deepFilter)",
+                "_queryParams('', 'flatFilter', flatFilter)");
+    }
+
     @Test(description = "Enum properties with defaults should emit enum constructor, not string literal")
     public void testEnumDefaultUsesEnumConstructor() throws Exception {
         List<File> files = generateDartNativeFromSpec(
diff --git a/samples/client/wildcard-accept-header/java/build.gradle b/samples/client/wildcard-accept-header/java/build.gradle
index 181c3a201e08..ce09e960be4d 100644
--- a/samples/client/wildcard-accept-header/java/build.gradle
+++ b/samples/client/wildcard-accept-header/java/build.gradle
@@ -24,6 +24,10 @@ sourceSets {
     main.java.srcDirs = ['src/main/java']
 }
 
+ext {
+    jakarta_annotation_version = "1.3.5"
+}
+
 if(hasProperty('target') && target == 'android') {
 
     apply plugin: 'com.android.library'
@@ -103,10 +107,6 @@ if(hasProperty('target') && target == 'android') {
     }
 }
 
-ext {
-    jakarta_annotation_version = "1.3.5"
-}
-
 dependencies {
     implementation "com.google.code.findbugs:jsr305:3.0.2"
     implementation 'com.squareup.okhttp3:okhttp:4.12.0'
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index c61373a87937..ab0713d278f6 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -1382,7 +1382,8 @@ class FakeApi {
       queryParams.addAll(_queryParams('csv', 'url', url));
       queryParams.addAll(_queryParams('multi', 'context', context));
     if (language != null) {
-      queryParams.addAll(_queryParams('', 'language', language));
+      // form style, explode: one query parameter per entry, keyed by the property name; a collection repeats the key per non-null element
+      language.forEach((entryKey, dynamic entryValue) => queryParams.addAll(_queryParams('multi', entryKey.toString(), entryValue is Iterable ? entryValue.where((e) => e != null).toList() : entryValue)));
     }
       queryParams.addAll(_queryParams('', 'allowEmpty', allowEmpty));