diff --git a/src/Api/GroupsMilestones.php b/src/Api/GroupsMilestones.php
index f870f78c..fad1c5d8 100644
--- a/src/Api/GroupsMilestones.php
+++ b/src/Api/GroupsMilestones.php
@@ -14,6 +14,8 @@
 
 namespace Gitlab\Api;
 
+use Symfony\Component\OptionsResolver\Options;
+
 class GroupsMilestones extends AbstractApi
 {
     /**
@@ -32,7 +34,9 @@ class GroupsMilestones extends AbstractApi
      *
      *     @var int[]  $iids   return only the milestones having the given iids
      *     @var string $state  return only active or closed milestones
-     *     @var string $search Return only milestones with a title or description matching the provided string.
+     *     @var string $search Return only milestones with a title or description matching the provided string
+     *     @var \DateTimeInterface $updated_after Return only milestones updated on or after the given datetime. Expected in ISO 8601 format (2019-03-15T08:00:00Z)
+     *     @var \DateTimeInterface $updated_before Return only milestones updated on or before the given datetime. Expected in ISO 8601 format (2019-03-15T08:00:00Z)
      * }
      *
      * @return mixed
@@ -40,6 +44,11 @@ class GroupsMilestones extends AbstractApi
     public function all($group_id, array $parameters = [])
     {
         $resolver = $this->createOptionsResolver();
+        $datetimeNormalizer = function (Options $resolver, \DateTimeInterface $value): string {
+            $utc = (new \DateTimeImmutable($value->format(\DateTimeImmutable::RFC3339_EXTENDED)))->setTimezone(new \DateTimeZone('UTC'));
+
+            return $utc->format('Y-m-d\TH:i:s.v\Z');
+        };
         $resolver->setDefined('iids')
             ->setAllowedTypes('iids', 'array')
             ->setAllowedValues('iids', function (array $value) {
@@ -51,6 +60,13 @@ public function all($group_id, array $parameters = [])
         ;
         $resolver->setDefined('search');
 
+        $resolver->setDefined('updated_after')
+            ->setAllowedTypes('updated_after', \DateTimeInterface::class)
+            ->setNormalizer('updated_after', $datetimeNormalizer);
+        $resolver->setDefined('updated_before')
+            ->setAllowedTypes('updated_before', \DateTimeInterface::class)
+            ->setNormalizer('updated_before', $datetimeNormalizer);
+
         return $this->get('groups/'.self::encodePath($group_id).'/milestones', $resolver->resolve($parameters));
     }
 
diff --git a/tests/Api/GroupsMilestonesTest.php b/tests/Api/GroupsMilestonesTest.php
index 3dc5d7a7..9fcd80cf 100644
--- a/tests/Api/GroupsMilestonesTest.php
+++ b/tests/Api/GroupsMilestonesTest.php
@@ -38,6 +38,106 @@ public function shouldGetAllMilestones(): void
         $this->assertEquals($expectedArray, $api->all(1));
     }
 
+    /**
+     * @test
+     */
+    public function shouldGetAllMilestonesWithParameterOneIidsValue(): void
+    {
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['iids' => [456]])
+        ;
+
+        $api->all(1, ['iids' => [456]]);
+    }
+
+    /**
+     * @test
+     */
+    public function shouldGetAllMilestonesWithParameterTwoIidsValues(): void
+    {
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['iids' => [456, 789]])
+        ;
+
+        $api->all(1, ['iids' => [456, 789]]);
+    }
+
+    public static function getAllMilestonesWithParameterStateDataProvider()
+    {
+        return [
+            GroupsMilestones::STATE_ACTIVE => [GroupsMilestones::STATE_ACTIVE],
+            GroupsMilestones::STATE_CLOSED => [GroupsMilestones::STATE_CLOSED],
+        ];
+    }
+
+    /**
+     * @test
+     *
+     * @dataProvider getAllMilestonesWithParameterStateDataProvider
+     */
+    public function shouldGetAllMilestonesWithParameterState(string $state): void
+    {
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['state' => $state])
+        ;
+
+        $api->all(1, ['state' => $state]);
+    }
+
+    /**
+     * @test
+     */
+    public function shouldGetAllMilestonesWithParameterSearch(): void
+    {
+        $searchValue = 'abc';
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['search' => $searchValue])
+        ;
+
+        $api->all(1, ['search' => $searchValue]);
+    }
+
+    /**
+     * @test
+     */
+    public function shouldGetAllMilestonesWithParameterUpdatedBefore(): void
+    {
+        $updatedBefore = new \DateTimeImmutable('2023-11-25T08:00:00Z');
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['updated_before' => '2023-11-25T08:00:00.000Z'])
+        ;
+
+        $api->all(1, ['updated_before' => $updatedBefore]);
+    }
+
+    /**
+     * @test
+     */
+    public function shouldGetAllMilestonesWithParameterUpdatedAfter(): void
+    {
+        $updatedAfter = new \DateTimeImmutable('2023-11-25T08:00:00Z');
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with('groups/1/milestones', ['updated_after' => '2023-11-25T08:00:00.000Z'])
+        ;
+
+        $api->all(1, ['updated_after' => $updatedAfter]);
+    }
+
     /**
      * @test
      */