diff --git a/osu.Game/IO/OsuStorage.cs b/osu.Game/IO/OsuStorage.cs
index f5ce1c0105..1d15294666 100644
--- a/osu.Game/IO/OsuStorage.cs
+++ b/osu.Game/IO/OsuStorage.cs
@@ -2,9 +2,11 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Threading;
+using JetBrains.Annotations;
 using osu.Framework.Logging;
 using osu.Framework.Platform;
 using osu.Game.Configuration;
@@ -13,12 +15,30 @@ namespace osu.Game.IO
 {
     public class OsuStorage : WrappedStorage
     {
+        /// <summary>
+        /// Indicates the error (if any) that occurred when initialising the custom storage during initial startup.
+        /// </summary>
+        public readonly OsuStorageError Error;
+
+        /// <summary>
+        /// The custom storage path as selected by the user.
+        /// </summary>
+        [CanBeNull]
+        public string CustomStoragePath => storageConfig.Get<string>(StorageConfig.FullPath);
+
+        /// <summary>
+        /// The default storage path to be used if a custom storage path hasn't been selected or is not accessible.
+        /// </summary>
+        [NotNull]
+        public string DefaultStoragePath => defaultStorage.GetFullPath(".");
+
         private readonly GameHost host;
         private readonly StorageConfigManager storageConfig;
+        private readonly Storage defaultStorage;
 
-        internal static readonly string[] IGNORE_DIRECTORIES = { "cache" };
+        public static readonly string[] IGNORE_DIRECTORIES = { "cache" };
 
-        internal static readonly string[] IGNORE_FILES =
+        public static readonly string[] IGNORE_FILES =
         {
             "framework.ini",
             "storage.ini"
@@ -28,13 +48,53 @@ namespace osu.Game.IO
             : base(defaultStorage, string.Empty)
         {
             this.host = host;
+            this.defaultStorage = defaultStorage;
 
             storageConfig = new StorageConfigManager(defaultStorage);
 
-            var customStoragePath = storageConfig.Get<string>(StorageConfig.FullPath);
+            if (!string.IsNullOrEmpty(CustomStoragePath))
+                TryChangeToCustomStorage(out Error);
+        }
 
-            if (!string.IsNullOrEmpty(customStoragePath))
-                ChangeTargetStorage(host.GetStorage(customStoragePath));
+        /// <summary>
+        /// Resets the custom storage path, changing the target storage to the default location.
+        /// </summary>
+        public void ResetCustomStoragePath()
+        {
+            storageConfig.Set(StorageConfig.FullPath, string.Empty);
+            storageConfig.Save();
+
+            ChangeTargetStorage(defaultStorage);
+        }
+
+        /// <summary>
+        /// Attempts to change to the user's custom storage path.
+        /// </summary>
+        /// <param name="error">The error that occurred.</param>
+        /// <returns>Whether the custom storage path was used successfully. If not, <paramref name="error"/> will be populated with the reason.</returns>
+        public bool TryChangeToCustomStorage(out OsuStorageError error)
+        {
+            Debug.Assert(!string.IsNullOrEmpty(CustomStoragePath));
+
+            error = OsuStorageError.None;
+            Storage lastStorage = UnderlyingStorage;
+
+            try
+            {
+                Storage userStorage = host.GetStorage(CustomStoragePath);
+
+                if (!userStorage.ExistsDirectory(".") || !userStorage.GetFiles(".").Any())
+                    error = OsuStorageError.AccessibleButEmpty;
+
+                ChangeTargetStorage(userStorage);
+            }
+            catch
+            {
+                error = OsuStorageError.NotAccessible;
+                ChangeTargetStorage(lastStorage);
+            }
+
+            return error == OsuStorageError.None;
         }
 
         protected override void ChangeTargetStorage(Storage newStorage)
@@ -145,4 +205,23 @@ namespace osu.Game.IO
             }
         }
     }
+
+    public enum OsuStorageError
+    {
+        /// <summary>
+        /// No error.
+        /// </summary>
+        None,
+
+        /// <summary>
+        /// Occurs when the target storage directory is accessible but does not already contain game files.
+        /// Only happens when the user changes the storage directory and then moves the files manually or mounts a different device to the same path.
+        /// </summary>
+        AccessibleButEmpty,
+
+        /// <summary>
+        /// Occurs when the target storage directory cannot be accessed at all.
+        /// </summary>
+        NotAccessible,
+    }
 }
diff --git a/osu.Game/Overlays/Dialog/PopupDialog.cs b/osu.Game/Overlays/Dialog/PopupDialog.cs
index 02ef900dc5..1bcbe4dd2f 100644
--- a/osu.Game/Overlays/Dialog/PopupDialog.cs
+++ b/osu.Game/Overlays/Dialog/PopupDialog.cs
@@ -42,25 +42,34 @@ namespace osu.Game.Overlays.Dialog
             set => icon.Icon = value;
         }
 
-        private string text;
+        private string headerText;
 
         public string HeaderText
         {
-            get => text;
+            get => headerText;
             set
             {
-                if (text == value)
+                if (headerText == value)
                     return;
 
-                text = value;
-
+                headerText = value;
                 header.Text = value;
             }
         }
 
+        private string bodyText;
+
         public string BodyText
         {
-            set => body.Text = value;
+            get => bodyText;
+            set
+            {
+                if (bodyText == value)
+                    return;
+
+                bodyText = value;
+                body.Text = value;
+            }
         }
 
         public IEnumerable<PopupDialogButton> Buttons
diff --git a/osu.Game/Screens/Menu/ConfirmExitDialog.cs b/osu.Game/Screens/Menu/ConfirmExitDialog.cs
new file mode 100644
index 0000000000..d120eb21a8
--- /dev/null
+++ b/osu.Game/Screens/Menu/ConfirmExitDialog.cs
@@ -0,0 +1,34 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.Overlays.Dialog;
+
+namespace osu.Game.Screens.Menu
+{
+    public class ConfirmExitDialog : PopupDialog
+    {
+        public ConfirmExitDialog(Action confirm, Action cancel)
+        {
+            HeaderText = "Are you sure you want to exit?";
+            BodyText = "Last chance to back out.";
+
+            Icon = FontAwesome.Solid.ExclamationTriangle;
+
+            Buttons = new PopupDialogButton[]
+            {
+                new PopupDialogOkButton
+                {
+                    Text = @"Goodbye",
+                    Action = confirm
+                },
+                new PopupDialogCancelButton
+                {
+                    Text = @"Just a little more",
+                    Action = cancel
+                },
+            };
+        }
+    }
+}
diff --git a/osu.Game/Screens/Menu/MainMenu.cs b/osu.Game/Screens/Menu/MainMenu.cs
index 9245df2a7d..76950982e6 100644
--- a/osu.Game/Screens/Menu/MainMenu.cs
+++ b/osu.Game/Screens/Menu/MainMenu.cs
@@ -1,7 +1,6 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System;
 using System.Linq;
 using osuTK;
 using osuTK.Graphics;
@@ -9,15 +8,14 @@ using osu.Framework.Allocation;
 using osu.Framework.Audio.Track;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
-using osu.Framework.Graphics.Sprites;
 using osu.Framework.Platform;
 using osu.Framework.Screens;
 using osu.Game.Configuration;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
+using osu.Game.IO;
 using osu.Game.Online.API;
 using osu.Game.Overlays;
-using osu.Game.Overlays.Dialog;
 using osu.Game.Screens.Backgrounds;
 using osu.Game.Screens.Edit;
 using osu.Game.Screens.Multi;
@@ -171,6 +169,9 @@ namespace osu.Game.Screens.Menu
             return s;
         }
 
+        [Resolved]
+        private Storage storage { get; set; }
+
         public override void OnEntering(IScreen last)
         {
             base.OnEntering(last);
@@ -187,6 +188,9 @@ namespace osu.Game.Screens.Menu
                     Track.Start();
                 }
             }
+
+            if (storage is OsuStorage osuStorage && osuStorage.Error != OsuStorageError.None)
+                dialogOverlay?.Push(new StorageErrorDialog(osuStorage, osuStorage.Error));
         }
 
         private bool exitConfirmed;
@@ -283,30 +287,5 @@ namespace osu.Game.Screens.Menu
             this.FadeOut(3000);
             return base.OnExiting(next);
         }
-
-        private class ConfirmExitDialog : PopupDialog
-        {
-            public ConfirmExitDialog(Action confirm, Action cancel)
-            {
-                HeaderText = "Are you sure you want to exit?";
-                BodyText = "Last chance to back out.";
-
-                Icon = FontAwesome.Solid.ExclamationTriangle;
-
-                Buttons = new PopupDialogButton[]
-                {
-                    new PopupDialogOkButton
-                    {
-                        Text = @"Goodbye",
-                        Action = confirm
-                    },
-                    new PopupDialogCancelButton
-                    {
-                        Text = @"Just a little more",
-                        Action = cancel
-                    },
-                };
-            }
-        }
     }
 }
diff --git a/osu.Game/Screens/Menu/StorageErrorDialog.cs b/osu.Game/Screens/Menu/StorageErrorDialog.cs
new file mode 100644
index 0000000000..dcaad4013a
--- /dev/null
+++ b/osu.Game/Screens/Menu/StorageErrorDialog.cs
@@ -0,0 +1,79 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics.Sprites;
+using osu.Game.IO;
+using osu.Game.Overlays;
+using osu.Game.Overlays.Dialog;
+
+namespace osu.Game.Screens.Menu
+{
+    public class StorageErrorDialog : PopupDialog
+    {
+        [Resolved]
+        private DialogOverlay dialogOverlay { get; set; }
+
+        [Resolved]
+        private OsuGameBase osuGame { get; set; }
+
+        public StorageErrorDialog(OsuStorage storage, OsuStorageError error)
+        {
+            HeaderText = "osu! storage error";
+            Icon = FontAwesome.Solid.ExclamationTriangle;
+
+            var buttons = new List<PopupDialogButton>();
+
+            switch (error)
+            {
+                case OsuStorageError.NotAccessible:
+                    BodyText = $"The specified osu! data location (\"{storage.CustomStoragePath}\") is not accessible. If it is on external storage, please reconnect the device and try again.";
+
+                    buttons.AddRange(new PopupDialogButton[]
+                    {
+                        new PopupDialogCancelButton
+                        {
+                            Text = "Try again",
+                            Action = () =>
+                            {
+                                if (!storage.TryChangeToCustomStorage(out var nextError))
+                                    dialogOverlay.Push(new StorageErrorDialog(storage, nextError));
+                            }
+                        },
+                        new PopupDialogCancelButton
+                        {
+                            Text = "Use default location until restart",
+                        },
+                        new PopupDialogOkButton
+                        {
+                            Text = "Reset to default location",
+                            Action = storage.ResetCustomStoragePath
+                        },
+                    });
+                    break;
+
+                case OsuStorageError.AccessibleButEmpty:
+                    BodyText = $"The specified osu! data location (\"{storage.CustomStoragePath}\") is empty. If you have moved the files, please close osu! and move them back.";
+
+                    // Todo: Provide the option to search for the files similar to migration.
+                    buttons.AddRange(new PopupDialogButton[]
+                    {
+                        new PopupDialogCancelButton
+                        {
+                            Text = "Start fresh at specified location"
+                        },
+                        new PopupDialogOkButton
+                        {
+                            Text = "Reset to default location",
+                            Action = storage.ResetCustomStoragePath
+                        },
+                    });
+
+                    break;
+            }
+
+            Buttons = buttons;
+        }
+    }
+}