diff --git a/public/main/announcements/announcements.php b/public/main/announcements/announcements.php
index d7c99971eb6..2a6138a3dd0 100644
--- a/public/main/announcements/announcements.php
+++ b/public/main/announcements/announcements.php
@@ -404,6 +404,21 @@
 
         $to = [];
         if (empty($group_id)) {
+            if (!empty($sessionId)) {
+                $userGroups = Container::getUsergroupRepository()->findBySession($session);
+                $groupSelectTitle = get_lang('Classes of session').' '.$session->getTitle();
+            } else {
+                $userGroups = Container::getUsergroupRepository()->findByCourse($course);
+                $groupSelectTitle = get_lang('Classes of course');
+            }
+
+            if (!empty($userGroups)) {
+                $groupSelect = ['' => get_lang('Select a class')];
+                foreach ($userGroups as $group) {
+                    $groupSelect[$group->getId()] = $group->getTitle();
+                }
+                $form->addSelect('usergroup_id', $groupSelectTitle, $groupSelect, ['id' => 'usergroup_id']);
+            }
             if (isset($_GET['remind_inactive'])) {
                 $email_ann = '1';
                 $content_to_modify = sprintf(
@@ -508,41 +523,88 @@
         }
 
         $ajaxUrl = api_get_path(WEB_AJAX_PATH).'announcement.ajax.php?'.api_get_cidreq().'&a=preview';
-
+        $ajaxUserGroupUrl = api_get_path(WEB_AJAX_PATH).'usergroup.ajax.php?'.api_get_cidreq();
         $form->addHtml("
-            <script>
-                $(function () {
-                    $('#announcement_preview').on('click', function() {
+        <script>
+            $(function () {
+                $('#usergroup_id').on('change', function () {
+                    const groupId = $(this).val();
+                    const selected = $('#users_to');
+                    selected.empty();
+                    if (!groupId) return;
+                    $.ajax({
+                        url: '".$ajaxUserGroupUrl."',
+                        type: 'POST',
+                        data: {
+                            a: 'get_users_by_group_course',
+                            group_id: groupId,
+                            course_code: '".api_get_course_id()."',
+                            session_id: '".api_get_session_id()."'
+                        },
+                        success: function (response) {
+                            const result = JSON.parse(response);
+                            for (let user of result) {
+                                selected.append(new Option(user.name, 'USER:' + user.id));
+                            }
+                            $('#announcement_preview_result').html('');
+                        }
+                    })
+                });
+
+                $('#announcement_preview').on('click', function () {
+                    const selectedClass = $('#usergroup_id').val();
+                    if (selectedClass) {
                         var users = [];
-                        $('#users_to option').each(function() {
+                        var userLabels = [];
+                        $('#users_to option').each(function () {
                             users.push($(this).val());
+                            userLabels.push($(this).text());
                         });
-
+                        if (users.length === 0) {
+                            $('#announcement_preview_result').html('');
+                            $('#announcement_preview_result').show();
+                            return;
+                        }
+                        var resultHtml = '<strong>".addslashes(get_lang('Announcement will be sent to'))."</strong><ul>';
+                        userLabels.forEach(function (name) {
+                            resultHtml += '<li>' + name + '</li>';
+                        });
+                        resultHtml += '</ul>';
+                        $('#announcement_preview_result').html(resultHtml);
+                        $('#announcement_preview_result').show();
+                        $('#send_button').show();
+                    } else {
+                        var users = [];
                         var form = $('#announcement').serialize();
+                        $('#users_to option').each(function () {
+                            users.push($(this).val());
+                        });
                         $.ajax({
                             type: 'POST',
                             dataType: 'json',
-                            url: '".$ajaxUrl."',
-                            data: {users : JSON.stringify(users), form: form},
-                            beforeSend: function() {
+                            url: '" . $ajaxUrl . "',
+                            data: {users: JSON.stringify(users), form: form},
+                            beforeSend: function () {
                                 $('#announcement_preview_result').html('<i class=\"fa fa-spinner\"></i>');
                                 $('#send_button').hide();
                             },
-                            success: function(result) {
-                                var resultToString = '';
-                                $.each(result, function(index, value) {
-                                    resultToString += '&nbsp;' + value;
-                                });
-                                $('#announcement_preview_result').html('' +
-                                    '".addslashes(get_lang('Announcement will be sent to'))."<br/>' + resultToString
+                            success: function (result) {
+                                let list = '<ul>';
+                                for (let name of result) {
+                                    list += '<li>' + name + '</li>';
+                                }
+                                list += '</ul>';
+                                $('#announcement_preview_result').html(
+                                    '<strong>".addslashes(get_lang('Announcement will be sent to'))."</strong><br>' + list
                                 );
                                 $('#announcement_preview_result').show();
                                 $('#send_button').show();
                             }
                         });
-                    });
+                    }
                 });
-            </script>
+            });
+        </script>
         ");
 
         if (isset($defaults['users'])) {
@@ -671,8 +733,7 @@
             $notificationPeriod = $data['notification_period'] ?? [];
 
             $reminders = $notificationCount ? array_map(null, $notificationCount, $notificationPeriod) : [];
-
-            if (isset($id) && $id) {
+            if (!empty($id)) {
                 // there is an Id => the announcement already exists => update mode
                 $file_comment = $announcementAttachmentIsDisabled ? null : $_POST['file_comment'];
                 $file = $announcementAttachmentIsDisabled ? [] : $_FILES['user_upload'];
diff --git a/public/main/inc/ajax/usergroup.ajax.php b/public/main/inc/ajax/usergroup.ajax.php
index 6ed36b7ccfe..5c3c0a85d17 100644
--- a/public/main/inc/ajax/usergroup.ajax.php
+++ b/public/main/inc/ajax/usergroup.ajax.php
@@ -5,12 +5,47 @@
 /**
  * Responses to AJAX calls.
  */
+
+use Chamilo\CoreBundle\Framework\Container;
+
 require_once __DIR__.'/../global.inc.php';
 
 $action = isset($_REQUEST['a']) ? $_REQUEST['a'] : '';
 $isAllowedToEdit = api_is_allowed_to_edit();
 
 switch ($action) {
+    case 'get_users_by_group_course':
+        $groupId = (int) $_POST['group_id'];
+        $sessionId = (int) $_POST['session_id'];
+        if ($groupId) {
+            $users = Container::getUsergroupRepository()->getUsersByGroup($groupId, true);
+            if (!empty($sessionId)) {
+                $filtered = [];
+                foreach ($users as $user) {
+                    $filtered[] = [
+                        'id' => $user['id'],
+                        'name' => api_get_person_name($user['firstname'], $user['lastname']),
+                    ];
+                }
+            } else {
+                $courseCode = $_POST['course_code'];
+                $courseUsers = CourseManager::get_user_list_from_course_code($courseCode, 0);
+                $courseUserIds = array_column($courseUsers, 'user_id');
+
+                $filtered = [];
+                foreach ($users as $user) {
+                    if (in_array($user['id'], $courseUserIds)) {
+                        $filtered[] = [
+                            'id' => $user['id'],
+                            'name' => api_get_person_name($user['firstname'], $user['lastname']),
+                        ];
+                    }
+                }
+            }
+
+            echo json_encode($filtered);
+        }
+        exit;
     case 'get_class_by_keyword':
         $keyword = isset($_REQUEST['q']) ? $_REQUEST['q'] : '';
         if (api_is_platform_admin() && !empty($keyword)) {
diff --git a/src/CoreBundle/Repository/Node/UsergroupRepository.php b/src/CoreBundle/Repository/Node/UsergroupRepository.php
index 3e43bd01f53..0be68a27c25 100644
--- a/src/CoreBundle/Repository/Node/UsergroupRepository.php
+++ b/src/CoreBundle/Repository/Node/UsergroupRepository.php
@@ -6,6 +6,8 @@
 
 namespace Chamilo\CoreBundle\Repository\Node;
 
+use Chamilo\CoreBundle\Entity\Course;
+use Chamilo\CoreBundle\Entity\Session;
 use Chamilo\CoreBundle\Entity\User;
 use Chamilo\CoreBundle\Entity\Usergroup;
 use Chamilo\CoreBundle\Entity\UsergroupRelUser;
@@ -24,6 +26,41 @@ public function __construct(
         parent::__construct($registry, Usergroup::class);
     }
 
+    public function findBySession(Session $session, bool $checkAccessUrl = false): array
+    {
+        $qb = $this->createQueryBuilder('ug')
+            ->innerJoin('ug.sessions', 'ugs')
+            ->where('ugs.session = :session')
+            ->setParameter('session', $session);
+
+        if ($checkAccessUrl && $this->accessUrlHelper->isMultiple()) {
+            $accessUrl = $this->accessUrlHelper->getCurrent();
+            $qb->innerJoin('ug.urls', 'url')
+                ->andWhere('url.url = :urlId')
+                ->setParameter('urlId', $accessUrl->getId());
+        }
+
+        return $qb->getQuery()->getResult();
+    }
+
+    public function findByCourse(Course $course, bool $checkAccessUrl = false): array
+    {
+        $qb = $this->createQueryBuilder('ug')
+            ->innerJoin('ug.courses', 'ugc')
+            ->where('ugc.course = :course')
+            ->setParameter('course', $course);
+
+        if ($checkAccessUrl && $this->accessUrlHelper->isMultiple()) {
+            $accessUrl = $this->accessUrlHelper->getCurrent();
+
+            $qb->innerJoin('ug.urls', 'url')
+                ->andWhere('url.url = :urlId')
+                ->setParameter('urlId', $accessUrl->getId());
+        }
+
+        return $qb->getQuery()->getResult();
+    }
+
     /**
      * @param int|array $relationType
      */
@@ -156,21 +193,27 @@ public function searchGroups(string $searchTerm): array
         return $queryBuilder->getQuery()->getResult();
     }
 
-    public function getUsersByGroup(int $groupID)
+    public function getUsersByGroup(int $groupID, bool $includeNormalClass = false): array
     {
         $qb = $this->createQueryBuilder('g')
             ->innerJoin('g.users', 'gu')
             ->innerJoin('gu.user', 'u')
             ->where('g.id = :groupID')
-            ->setParameter('groupID', $groupID)
-            ->andWhere('gu.relationType IN (:relationTypes)')
-            ->setParameter('relationTypes', [
-                Usergroup::GROUP_USER_PERMISSION_ADMIN,
-                Usergroup::GROUP_USER_PERMISSION_READER,
-                Usergroup::GROUP_USER_PERMISSION_PENDING_INVITATION,
-            ])
-            ->select('u.id, u.username, u.email, gu.relationType, u.pictureUri')
-        ;
+            ->setParameter('groupID', $groupID);
+
+        $relationTypes = [
+            Usergroup::GROUP_USER_PERMISSION_ADMIN,
+            Usergroup::GROUP_USER_PERMISSION_READER,
+            Usergroup::GROUP_USER_PERMISSION_PENDING_INVITATION,
+        ];
+
+        if ($includeNormalClass) {
+            $relationTypes[] = 0;
+        }
+
+        $qb->andWhere('gu.relationType IN (:relationTypes)')
+            ->setParameter('relationTypes', $relationTypes)
+            ->select('u.id, u.username, u.email, gu.relationType, u.pictureUri, u.firstname, u.lastname');
 
         $results = $qb->getQuery()->getResult();