diff --git a/src/Umbraco.Web/Editors/ContentTypeControllerBase.cs b/src/Umbraco.Web/Editors/ContentTypeControllerBase.cs
index 6ac936961f..e4a5b2e417 100644
--- a/src/Umbraco.Web/Editors/ContentTypeControllerBase.cs
+++ b/src/Umbraco.Web/Editors/ContentTypeControllerBase.cs
@@ -454,10 +454,12 @@ namespace Umbraco.Web.Editors
             var validateAttempt = service.ValidateComposition(composition);
             if (validateAttempt == false)
             {
-                //if it's not successful then we need to return some model state for the property aliases that
-                // are duplicated
-                var invalidPropertyAliases = validateAttempt.Result.Distinct();
-                AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(contentTypeSave, invalidPropertyAliases);
+                // if it's not successful then we need to return some model state for the property type and property group
+                // aliases that are duplicated
+                var invalidPropertyTypeAliases = validateAttempt.Result.Distinct();
+                var invalidPropertyGroupAliases = (validateAttempt.Exception as InvalidCompositionException)?.PropertyGroupAliases ?? Array.Empty<string>();
+
+                AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(contentTypeSave, invalidPropertyTypeAliases, invalidPropertyGroupAliases);
 
                 var display = Mapper.Map<TContentTypeDisplay>(composition);
                 //map the 'save' data on top
@@ -472,22 +474,32 @@ namespace Umbraco.Web.Editors
         /// Adds errors to the model state if any invalid aliases are found then throws an error response if there are errors
         /// </summary>
         /// <param name="contentTypeSave"></param>
-        /// <param name="invalidPropertyAliases"></param>
+        /// <param name="invalidPropertyTypeAliases"></param>
+        /// <param name="invalidPropertyGroupAliases"></param>
         /// <returns></returns>
-        private void AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(TContentTypeSave contentTypeSave, IEnumerable<string> invalidPropertyAliases)
+        private void AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(TContentTypeSave contentTypeSave, IEnumerable<string> invalidPropertyTypeAliases, IEnumerable<string> invalidPropertyGroupAliases)
             where TContentTypeSave : ContentTypeSave<TPropertyType>
             where TPropertyType : PropertyTypeBasic
         {
-            foreach (var propertyAlias in invalidPropertyAliases)
+            foreach (var propertyTypeAlias in invalidPropertyTypeAliases)
             {
-                // Find the property relating to these
-                var property = contentTypeSave.Groups.SelectMany(x => x.Properties).Single(x => x.Alias == propertyAlias);
+                // Find the property type relating to these
+                var property = contentTypeSave.Groups.SelectMany(x => x.Properties).Single(x => x.Alias == propertyTypeAlias);
                 var group = contentTypeSave.Groups.Single(x => x.Properties.Contains(property));
                 var propertyIndex = group.Properties.IndexOf(property);
                 var groupIndex = contentTypeSave.Groups.IndexOf(group);
 
                 var key = $"Groups[{groupIndex}].Properties[{propertyIndex}].Alias";
-                ModelState.AddModelError(key, "Duplicate property aliases not allowed between compositions");
+                ModelState.AddModelError(key, "Duplicate property aliases are not allowed between compositions");
+            }
+
+            foreach (var propertyGroupAlias in invalidPropertyGroupAliases)
+            {
+                // Find the property group relating to these
+                var group = contentTypeSave.Groups.Single(x => x.Alias == propertyGroupAlias);
+                var groupIndex = contentTypeSave.Groups.IndexOf(group);
+                var key = $"Groups[{groupIndex}].Name";
+                ModelState.AddModelError(key, "Duplicate property group aliases are not allowed between compositions");
             }
         }
 
@@ -519,7 +531,7 @@ namespace Umbraco.Web.Editors
             }
             if (invalidCompositionException != null)
             {
-                AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(contentTypeSave, invalidCompositionException.PropertyTypeAliases);
+                AddCompositionValidationErrors<TContentTypeSave, TPropertyType>(contentTypeSave, invalidCompositionException.PropertyTypeAliases, invalidCompositionException.PropertyGroupAliases);
                 return CreateModelStateValidationException<TContentTypeSave, TContentTypeDisplay>(ctId, contentTypeSave, ct);
             }
             return null;