diff --git a/bitwarden_license/src/Scim/Groups/PatchGroupCommandvNext.cs b/bitwarden_license/src/Scim/Groups/PatchGroupCommandvNext.cs
index 537f9a61f5fd..703f3061019f 100644
--- a/bitwarden_license/src/Scim/Groups/PatchGroupCommandvNext.cs
+++ b/bitwarden_license/src/Scim/Groups/PatchGroupCommandvNext.cs
@@ -87,7 +87,7 @@ private async Task HandleOperationAsync(Group group, ScimPatchModel.OperationMod
             case PatchOps.Add when
                 operation.Path?.ToLowerInvariant() == PatchPaths.Members:
                 {
-                    await AddMembersAsync(group, GetOperationValueIds(operation.Value).ToHashSet());
+                    await AddMembersAsync(group, GetOperationValueIds(operation.Value));
                     break;
                 }
 
@@ -122,20 +122,19 @@ private async Task HandleOperationAsync(Group group, ScimPatchModel.OperationMod
         }
     }
 
-    private async Task AddMembersAsync(Group group, HashSet<Guid> usersToAdd)
+    private async Task AddMembersAsync(Group group, List<Guid> usersToAdd)
     {
         // Azure Entra ID is known to send redundant "add" requests for each existing member every time any member
-        // is removed. To avoid excessive load on the database we detect these and return early.
+        // is removed. To avoid excessive load on the database, we check against the high availability replica and
+        // return early if they already exist.
         var groupMembers = await _groupRepository.GetManyUserIdsByIdAsync(group.Id, useReadOnlyReplica: true);
-        if (usersToAdd.IsSubsetOf(groupMembers))
+        if (usersToAdd.ToHashSet().IsSubsetOf(groupMembers))
         {
             _logger.LogDebug("Ignoring duplicate SCIM request to add members {Members} to group {Group}", usersToAdd, group.Id);
             return;
         }
 
-        // TODO: don't use the results of the previous query, just write a new upsert operation
-        var updatedMembers = groupMembers.Concat(usersToAdd).ToHashSet();
-        await _groupRepository.UpdateUsersAsync(group.Id, updatedMembers);
+        await _groupRepository.AddGroupUsersByIdAsync(group.Id, usersToAdd);
     }
 
     private List<Guid> GetOperationValueIds(JsonElement objArray)
diff --git a/src/Core/AdminConsole/Repositories/IGroupRepository.cs b/src/Core/AdminConsole/Repositories/IGroupRepository.cs
index 62cc5052e7e5..27a00e011d90 100644
--- a/src/Core/AdminConsole/Repositories/IGroupRepository.cs
+++ b/src/Core/AdminConsole/Repositories/IGroupRepository.cs
@@ -28,6 +28,13 @@ Task<ICollection<Tuple<Group, ICollection<CollectionAccessSelection>>>> GetManyW
     Task CreateAsync(Group obj, IEnumerable<CollectionAccessSelection> collections);
     Task ReplaceAsync(Group obj, IEnumerable<CollectionAccessSelection> collections);
     Task DeleteUserAsync(Guid groupId, Guid organizationUserId);
+    /// <summary>
+    /// Update a group's members. Replaces all members currently in the group.
+    /// </summary>
     Task UpdateUsersAsync(Guid groupId, IEnumerable<Guid> organizationUserIds);
+    /// <summary>
+    /// Add members to a group. Ignores members that are already in the group.
+    /// </summary>
+    Task AddGroupUsersByIdAsync(Guid groupId, IEnumerable<Guid> organizationUserIds);
     Task DeleteManyAsync(IEnumerable<Guid> groupIds);
 }
diff --git a/src/Infrastructure.Dapper/AdminConsole/Repositories/GroupRepository.cs b/src/Infrastructure.Dapper/AdminConsole/Repositories/GroupRepository.cs
index 6287507dc9da..ebac7eec952c 100644
--- a/src/Infrastructure.Dapper/AdminConsole/Repositories/GroupRepository.cs
+++ b/src/Infrastructure.Dapper/AdminConsole/Repositories/GroupRepository.cs
@@ -190,6 +190,17 @@ public async Task UpdateUsersAsync(Guid groupId, IEnumerable<Guid> organizationU
         }
     }
 
+    public async Task AddGroupUsersByIdAsync(Guid groupId, IEnumerable<Guid> organizationUserIds)
+    {
+        using (var connection = new SqlConnection(ConnectionString))
+        {
+            var results = await connection.ExecuteAsync(
+                "[dbo].[GroupUser_UpsertUsers]",
+                new { GroupId = groupId, OrganizationUserIds = organizationUserIds.ToGuidIdArrayTVP() },
+                commandType: CommandType.StoredProcedure);
+        }
+    }
+
     public async Task DeleteManyAsync(IEnumerable<Guid> groupIds)
     {
         using (var connection = new SqlConnection(ConnectionString))
diff --git a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/GroupRepository.cs b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/GroupRepository.cs
index 35d486ca45b2..305a715d4c34 100644
--- a/src/Infrastructure.EntityFramework/AdminConsole/Repositories/GroupRepository.cs
+++ b/src/Infrastructure.EntityFramework/AdminConsole/Repositories/GroupRepository.cs
@@ -257,6 +257,29 @@ where organizationUserIds.Contains(ou.Id) &&
         }
     }
 
+    public async Task AddGroupUsersByIdAsync(Guid groupId, IEnumerable<Guid> organizationUserIds)
+    {
+        using (var scope = ServiceScopeFactory.CreateScope())
+        {
+            var dbContext = GetDatabaseContext(scope);
+            var orgId = (await dbContext.Groups.FindAsync(groupId)).OrganizationId;
+            var insert = from ou in dbContext.OrganizationUsers
+                         where organizationUserIds.Contains(ou.Id) &&
+                             ou.OrganizationId == orgId &&
+                             !dbContext.GroupUsers.Any(gu => gu.GroupId == groupId && ou.Id == gu.OrganizationUserId)
+                         select new GroupUser
+                         {
+                             GroupId = groupId,
+                             OrganizationUserId = ou.Id,
+                         };
+            await dbContext.AddRangeAsync(insert);
+
+            await dbContext.SaveChangesAsync();
+            await dbContext.UserBumpAccountRevisionDateByOrganizationIdAsync(orgId);
+            await dbContext.SaveChangesAsync();
+        }
+    }
+
     public async Task DeleteManyAsync(IEnumerable<Guid> groupIds)
     {
         using (var scope = ServiceScopeFactory.CreateScope())
diff --git a/src/Sql/dbo/Stored Procedures/GroupUser_AddUsers.sql b/src/Sql/dbo/Stored Procedures/GroupUser_AddUsers.sql
new file mode 100644
index 000000000000..1b6e799fee0e
--- /dev/null
+++ b/src/Sql/dbo/Stored Procedures/GroupUser_AddUsers.sql	
@@ -0,0 +1,39 @@
+CREATE PROCEDURE [dbo].[GroupUser_UpdateUsers]
+    @GroupId UNIQUEIDENTIFIER,
+    @OrganizationUserIds AS [dbo].[GuidIdArray] READONLY
+AS
+BEGIN
+    SET NOCOUNT ON
+
+    DECLARE @OrgId UNIQUEIDENTIFIER = (
+        SELECT TOP 1
+            [OrganizationId]
+        FROM
+            [dbo].[Group]
+        WHERE
+            [Id] = @GroupId
+    )
+
+    -- Insert
+    INSERT INTO
+        [dbo].[GroupUser]
+    SELECT
+        @GroupId,
+        [Source].[Id]
+    FROM
+        @OrganizationUserIds AS [Source]
+    INNER JOIN
+        [dbo].[OrganizationUser] OU ON [Source].[Id] = OU.[Id] AND OU.[OrganizationId] = @OrgId
+    WHERE
+        NOT EXISTS (
+            SELECT
+                1
+            FROM
+                [dbo].[GroupUser]
+            WHERE
+                [GroupId] = @GroupId
+                AND [OrganizationUserId] = [Source].[Id]
+        )
+
+    EXEC [dbo].[User_BumpAccountRevisionDateByOrganizationId] @OrgId
+END
diff --git a/util/Migrator/DbScripts/2025-02-03_00_GroupUser_AddUsers.sql b/util/Migrator/DbScripts/2025-02-03_00_GroupUser_AddUsers.sql
new file mode 100644
index 000000000000..e1baef23b7d3
--- /dev/null
+++ b/util/Migrator/DbScripts/2025-02-03_00_GroupUser_AddUsers.sql
@@ -0,0 +1,39 @@
+CREATE OR ALTER PROCEDURE [dbo].[GroupUser_UpdateUsers]
+    @GroupId UNIQUEIDENTIFIER,
+    @OrganizationUserIds AS [dbo].[GuidIdArray] READONLY
+AS
+BEGIN
+    SET NOCOUNT ON
+
+    DECLARE @OrgId UNIQUEIDENTIFIER = (
+        SELECT TOP 1
+            [OrganizationId]
+        FROM
+            [dbo].[Group]
+        WHERE
+            [Id] = @GroupId
+    )
+
+    -- Insert
+    INSERT INTO
+        [dbo].[GroupUser]
+    SELECT
+        @GroupId,
+        [Source].[Id]
+    FROM
+        @OrganizationUserIds AS [Source]
+    INNER JOIN
+        [dbo].[OrganizationUser] OU ON [Source].[Id] = OU.[Id] AND OU.[OrganizationId] = @OrgId
+    WHERE
+        NOT EXISTS (
+            SELECT
+                1
+            FROM
+                [dbo].[GroupUser]
+            WHERE
+                [GroupId] = @GroupId
+                AND [OrganizationUserId] = [Source].[Id]
+        )
+
+    EXEC [dbo].[User_BumpAccountRevisionDateByOrganizationId] @OrgId
+END