diff --git a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
index cca8fe10..b8c0176a 100644
--- a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
+++ b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
@@ -49,7 +49,7 @@ public partial class ModEditWindow
 
         /// <inheritdoc/>
         public bool Valid
-            => Mdl.Valid;
+            => Mdl.Valid && Mdl.Materials.All(ValidateMaterial);
 
         /// <inheritdoc/>
         public byte[] Write()
@@ -285,6 +285,17 @@ public partial class ModEditWindow
                 : _edit._gameData.GetFile(resolvedPath.InternalName.ToString())?.Data;
         }
 
+        /// <summary> Validate the specified material. </summary>
+        /// <remarks>
+        /// While materials can be relative (`/mt_...`) or absolute (`bg/...`),
+        /// they invariably must contain at least one directory seperator.
+        /// Missing this can lead to a crash.
+        /// </remarks>
+        public bool ValidateMaterial(string material)
+        {
+            return material.Contains('/');
+        }
+
         /// <summary> Remove the material given by the index. </summary>
         /// <remarks> Meshes using the removed material are redirected to material 0, and those after the index are corrected. </remarks>
         public void RemoveMaterial(int materialIndex)
diff --git a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.cs b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.cs
index 6cd9b912..1cfa7585 100644
--- a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.cs
+++ b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.cs
@@ -1,4 +1,5 @@
 using Dalamud.Interface;
+using Dalamud.Interface.Components;
 using ImGuiNET;
 using OtterGui;
 using OtterGui.Custom;
@@ -295,7 +296,7 @@ public partial class ModEditWindow
         if (!ImGui.CollapsingHeader("Materials"))
             return false;
 
-        using var table = ImRaii.Table(string.Empty, disabled ? 2 : 3, ImGuiTableFlags.SizingFixedFit);
+        using var table = ImRaii.Table(string.Empty, disabled ? 2 : 4, ImGuiTableFlags.SizingFixedFit);
         if (!table)
             return false;
 
@@ -305,7 +306,10 @@ public partial class ModEditWindow
         ImGui.TableSetupColumn("index", ImGuiTableColumnFlags.WidthFixed,   80 * UiHelpers.Scale);
         ImGui.TableSetupColumn("path",  ImGuiTableColumnFlags.WidthStretch, 1);
         if (!disabled)
+        {
             ImGui.TableSetupColumn("actions", ImGuiTableColumnFlags.WidthFixed, UiHelpers.IconButtonSize.X);
+            ImGui.TableSetupColumn("help", ImGuiTableColumnFlags.WidthFixed, UiHelpers.IconButtonSize.X);
+        }
 
         var inputFlags = disabled ? ImGuiInputTextFlags.ReadOnly : ImGuiInputTextFlags.None;
         for (var materialIndex = 0; materialIndex < materials.Length; materialIndex++)
@@ -321,12 +325,15 @@ public partial class ModEditWindow
         ImGui.InputTextWithHint("##newMaterial", "Add new material...", ref _modelNewMaterial, Utf8GamePath.MaxGamePathLength, inputFlags);
         var validName = _modelNewMaterial.Length > 0 && _modelNewMaterial[0] == '/';
         ImGui.TableNextColumn();
-        if (!ImGuiUtil.DrawDisabledButton(FontAwesomeIcon.Plus.ToIconString(), UiHelpers.IconButtonSize, string.Empty, !validName, true))
-            return ret;
+        if (ImGuiUtil.DrawDisabledButton(FontAwesomeIcon.Plus.ToIconString(), UiHelpers.IconButtonSize, string.Empty, !validName, true))
+        {
+            ret |= true;
+            tab.Mdl.Materials = materials.AddItem(_modelNewMaterial);
+            _modelNewMaterial = string.Empty;
+        }
+        ImGui.TableNextColumn();
 
-        tab.Mdl.Materials = materials.AddItem(_modelNewMaterial);
-        _modelNewMaterial = string.Empty;
-        return true;
+        return ret;
     }
 
     private bool DrawMaterialRow(MdlTab tab, bool disabled, string[] materials, int materialIndex, ImGuiInputTextFlags inputFlags)
@@ -353,20 +360,33 @@ public partial class ModEditWindow
             return ret;
 
         ImGui.TableNextColumn();
-
         // Need to have at least one material.
-        if (materials.Length <= 1)
-            return ret;
+        if (materials.Length > 1)
+        {
+            var tt             = "Delete this material.\nAny meshes targeting this material will be updated to use material #1.";
+            var modifierActive = _config.DeleteModModifier.IsActive();
+            if (!modifierActive)
+                tt += $"\nHold {_config.DeleteModModifier} to delete.";
 
-        var tt             = "Delete this material.\nAny meshes targeting this material will be updated to use material #1.";
-        var modifierActive = _config.DeleteModModifier.IsActive();
-        if (!modifierActive)
-            tt += $"\nHold {_config.DeleteModModifier} to delete.";
-        if (!ImGuiUtil.DrawDisabledButton(FontAwesomeIcon.Trash.ToIconString(), UiHelpers.IconButtonSize, tt, !modifierActive, true))
-            return ret;
+            if (ImGuiUtil.DrawDisabledButton(FontAwesomeIcon.Trash.ToIconString(), UiHelpers.IconButtonSize, tt, !modifierActive, true))
+            {
+                tab.RemoveMaterial(materialIndex);
+                ret |= true;
+            }
+        }
 
-        tab.RemoveMaterial(materialIndex);
-        return true;
+        ImGui.TableNextColumn();
+        // Add markers to invalid materials.
+        if (!tab.ValidateMaterial(temp))
+            using (var colorHandle = ImRaii.PushColor(ImGuiCol.TextDisabled, 0xFF0000FF, true))
+            {
+                ImGuiComponents.HelpMarker(
+                    "Materials must be either relative (e.g. \"/filename.mtrl\")\n"
+                  + "or absolute (e.g. \"chara/full/path/to/filename.mtrl\").",
+                  FontAwesomeIcon.TimesCircle);
+            }
+        
+        return ret;
     }
 
     private bool DrawModelLodDetails(MdlTab tab, int lodIndex, bool disabled)