diff --git a/EXILED/Exiled.Permissions/Config.cs b/EXILED/Exiled.Permissions/Config.cs
index b0aabc52f0..81cf8fb394 100644
--- a/EXILED/Exiled.Permissions/Config.cs
+++ b/EXILED/Exiled.Permissions/Config.cs
@@ -44,6 +44,12 @@ public Config()
         [Description("The permissions full path")]
         public string FullPath { get; private set; }
 
+        /// <summary>
+        /// Gets a value indicating whether multi-group system should be used.
+        /// </summary>
+        [Description("Whether MultiGroup system should be used")]
+        public bool UseMultiGroup { get; private set; } = false;
+
         /// <inheritdoc/>
         public bool IsEnabled { get; set; } = true;
 
diff --git a/EXILED/Exiled.Permissions/Extensions/Permissions.cs b/EXILED/Exiled.Permissions/Extensions/Permissions.cs
index 56823e3feb..8127cca42e 100644
--- a/EXILED/Exiled.Permissions/Extensions/Permissions.cs
+++ b/EXILED/Exiled.Permissions/Extensions/Permissions.cs
@@ -14,16 +14,14 @@ namespace Exiled.Permissions.Extensions
     using System.Text;
 
     using CommandSystem;
-
     using Exiled.API.Extensions;
     using Exiled.API.Features;
     using Exiled.API.Features.Pools;
     using Features;
-
+    using Features.MultipleGroups;
     using Properties;
     using Query;
     using RemoteAdmin;
-
     using YamlDotNet.Core;
     using YamlDotNet.Serialization;
     using YamlDotNet.Serialization.NamingConventions;
@@ -207,15 +205,48 @@ public static bool CheckPermission(this Player player, string permission)
             Log.Debug($"UserID: {player.UserId} | PlayerId: {player.Id}");
             Log.Debug($"Permission string: {permission}");
 
-            string plyGroupKey = player.Group is not null ? ServerStatic.PermissionsHandler.Groups.FirstOrDefault(g => g.Value.EqualsTo(player.Group)).Key : null;
-            Log.Debug($"GroupKey: {plyGroupKey ?? "(null)"}");
+            if (!MultiGroup.IsActive)
+            {
+                string plyGroupKey = player.Group is not null ? ServerStatic.PermissionsHandler.Groups.FirstOrDefault(g => g.Value.EqualsTo(player.Group)).Key : null;
+                Log.Debug($"GroupKey: {plyGroupKey ?? "(null)"}");
+
+                if (plyGroupKey is null || !Groups.TryGetValue(plyGroupKey, out Group group))
+                {
+                    Log.Debug("The source group is null, the default group is used");
+                    group = DefaultGroup;
+                }
+
+                return group.CheckPermission(permission);
+            }
+
+            if (!MultiGroup.Permissions.TryGetValue(player.UserId, out string[] data))
+                return false;
 
-            if (plyGroupKey is null || !Groups.TryGetValue(plyGroupKey, out Group group))
+            foreach (string group in data)
             {
-                Log.Debug("The source group is null, the default group is used");
-                group = DefaultGroup;
+                if (!Groups.TryGetValue(group, out Group value))
+                {
+                    Log.Error($"Invalid group name: {group}");
+                    continue;
+                }
+
+                if (value.CheckPermission(permission))
+                    return true;
             }
 
+            return false;
+        }
+
+        /// <summary>
+        /// Checks a group's permission.
+        /// </summary>
+        /// <param name="group">The group to be checked.</param>
+        /// <param name="permission">The permission to be checked.</param>
+        /// <returns><see langword="true"/> if the player's current or native group has permissions; otherwise, <see langword="false"/>.</returns>
+        public static bool CheckPermission(this Group group, string permission)
+        {
+            group ??= DefaultGroup;
+
             if (group is null)
             {
                 Log.Debug("There's no default group, returning false...");
diff --git a/EXILED/Exiled.Permissions/Features/MultipleGroups/BaseCheckPatch.cs b/EXILED/Exiled.Permissions/Features/MultipleGroups/BaseCheckPatch.cs
new file mode 100644
index 0000000000..26520cc305
--- /dev/null
+++ b/EXILED/Exiled.Permissions/Features/MultipleGroups/BaseCheckPatch.cs
@@ -0,0 +1,81 @@
+// -----------------------------------------------------------------------
+// <copyright file="BaseCheckPatch.cs" company="ExMod Team">
+// Copyright (c) ExMod Team. All rights reserved.
+// Licensed under the CC BY-SA 3.0 license.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Exiled.Permissions.Features.MultipleGroups
+{
+    using System.Collections.Generic;
+    using System.Reflection.Emit;
+
+    using CommandSystem;
+    using Exiled.API.Features;
+    using HarmonyLib;
+    using Query;
+    using RemoteAdmin;
+
+    /// <summary>
+    /// Patches base-game method to implement multiple groups check per user.
+    /// </summary>
+    [HarmonyPatch]
+    internal static class BaseCheckPatch
+    {
+        private static bool Check(ICommandSender sender, PlayerPermissions[] permissions)
+        {
+            if (sender is not CommandSender commandSender)
+                return false;
+
+            if (commandSender.FullPermissions || sender is ServerConsoleSender || commandSender == Server.Host.Sender)
+            {
+                return true;
+            }
+
+            if (sender is PlayerCommandSender || sender is QueryCommandSender)
+            {
+                if (!Player.TryGet(sender, out Player player))
+                    return false;
+
+                if (!MultiGroup.Permissions.TryGetValue(player.UserId, out string[] data))
+                    return false;
+
+                foreach (string groupName in data)
+                {
+                    UserGroup group = ServerStatic.PermissionsHandler.GetGroup(groupName);
+                    if (group == null)
+                    {
+                        Log.Error($"Invalid group name: {groupName}");
+                        continue;
+                    }
+
+                    if (PermissionsHandler.IsPermitted(group.Permissions, permissions))
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static bool Check(ICommandSender sender, PlayerPermissions permissions) => Check(sender, new[] { permissions });
+
+        [HarmonyPatch(typeof(Misc), nameof(Misc.CheckPermission), typeof(ICommandSender), typeof(PlayerPermissions))]
+        private static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> instructions)
+        {
+            yield return new(OpCodes.Ldarg_0);
+            yield return new(OpCodes.Ldarg_1);
+            yield return new(OpCodes.Call, AccessTools.Method(typeof(BaseCheckPatch), nameof(Check), new[] { typeof(ICommandSender),  typeof(PlayerPermissions) }));
+            yield return new(OpCodes.Ret);
+        }
+
+        [HarmonyTranspiler]
+        [HarmonyPatch(typeof(Misc), nameof(Misc.CheckPermission), typeof(ICommandSender), typeof(PlayerPermissions[]))]
+        private static IEnumerable<CodeInstruction> TranspilerMore(IEnumerable<CodeInstruction> instructions)
+        {
+            yield return new(OpCodes.Ldarg_0);
+            yield return new(OpCodes.Ldarg_1);
+            yield return new(OpCodes.Call, AccessTools.Method(typeof(BaseCheckPatch), nameof(Check), new[] { typeof(ICommandSender),  typeof(PlayerPermissions[]) }));
+            yield return new(OpCodes.Ret);
+        }
+    }
+}
\ No newline at end of file
diff --git a/EXILED/Exiled.Permissions/Features/MultipleGroups/MultiGroup.cs b/EXILED/Exiled.Permissions/Features/MultipleGroups/MultiGroup.cs
new file mode 100644
index 0000000000..01601b6d5d
--- /dev/null
+++ b/EXILED/Exiled.Permissions/Features/MultipleGroups/MultiGroup.cs
@@ -0,0 +1,105 @@
+// -----------------------------------------------------------------------
+// <copyright file="MultiGroup.cs" company="ExMod Team">
+// Copyright (c) ExMod Team. All rights reserved.
+// Licensed under the CC BY-SA 3.0 license.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Exiled.Permissions.Features.MultipleGroups
+{
+#pragma warning disable SA1401
+    using System;
+    using System.Collections.Generic;
+
+    using Exiled.API.Features;
+    using Exiled.API.Features.Pools;
+
+    using HarmonyLib;
+
+    /// <summary>
+    /// Main class for Multi-Group system.
+    /// </summary>
+    public static class MultiGroup
+    {
+        /// <summary>
+        /// A value indicating whether the system is active.
+        /// </summary>
+        internal static bool IsActive = false;
+
+        /// <summary>
+        /// Internal harmony instance.
+        /// </summary>
+        private static Harmony harmony;
+
+        /// <summary>
+        /// Gets a collection of all groups of all users.
+        /// </summary>
+        public static Dictionary<string, string[]> Permissions { get; private set; }
+
+        /// <summary>
+        /// Main method for initializing MultiGroup.
+        /// </summary>
+        /// <param name="force">Whether the load should be forced, ignoring config.</param>
+        public static void Init(bool force = false) // TODO: add list pooling
+        {
+            if (!Exiled.Permissions.Permissions.Instance.Config.UseMultiGroup && !force)
+                return;
+
+            List<string> groups = ServerStatic.PermissionsHandler._config.GetStringList("AdditionalGroups");
+            Dictionary<string, List<string>> users = new();
+
+            foreach (string entry in groups)
+            {
+                if (!entry.Contains(": "))
+                {
+                    Log.Error($"Invalid entry at AdditionalGroups in config_remoteadmin.txt: {entry}");
+                    continue;
+                }
+
+                int length = entry.IndexOf(": ", StringComparison.Ordinal);
+                string key = entry.Substring(0, length);
+                string value = entry.Substring(length + 2);
+
+                users.GetOrAdd(key, () => ListPool<string>.Pool.Get()).Add(value);
+            }
+
+            if (users.Count == 0)
+                return;
+
+            try
+            {
+                harmony = new("exiled.permissions-multigroups");
+                harmony.CreateClassProcessor(typeof(BaseCheckPatch)).Patch();
+            }
+            catch (HarmonyException exception)
+            {
+                Log.Error($"Patch error while patching for MultiGroups! {exception}");
+                return;
+            }
+
+            IsActive = true;
+            Permissions = new();
+
+            foreach (KeyValuePair<string, List<string>> kvp in users)
+            {
+                if (ServerStatic.PermissionsHandler.Members.TryGetValue(kvp.Key, out string group))
+                    kvp.Value.Add(group);
+
+                Permissions[kvp.Key] = ListPool<string>.Pool.ToArrayReturn(kvp.Value);
+            }
+        }
+
+        /// <summary>
+        /// Disables module and frees all resources.
+        /// </summary>
+        public static void Disable()
+        {
+            if (!IsActive)
+                return;
+
+            IsActive = false;
+            harmony.UnpatchAll("exiled.permissions-multigroups");
+            Permissions.Clear();
+        }
+    }
+}
\ No newline at end of file
diff --git a/EXILED/Exiled.Permissions/Permissions.cs b/EXILED/Exiled.Permissions/Permissions.cs
index eceb43810d..a279ac148e 100644
--- a/EXILED/Exiled.Permissions/Permissions.cs
+++ b/EXILED/Exiled.Permissions/Permissions.cs
@@ -8,6 +8,7 @@
 namespace Exiled.Permissions
 {
     using Exiled.API.Features;
+    using Features.MultipleGroups;
 
     using MEC;
 
@@ -36,12 +37,16 @@ public override void OnEnabled()
                 {
                     Extensions.Permissions.Create();
                     Extensions.Permissions.Reload();
+
+                    MultiGroup.Init();
                 });
         }
 
         /// <inheritdoc/>
         public override void OnDisabled()
         {
+            MultiGroup.Disable();
+
             base.OnDisabled();
 
             Extensions.Permissions.Groups.Clear();