diff --git a/source/blender/asset_system/AS_asset_catalog.hh b/source/blender/asset_system/AS_asset_catalog.hh
index 025a336cbd4..d9115644c2e 100644
--- a/source/blender/asset_system/AS_asset_catalog.hh
+++ b/source/blender/asset_system/AS_asset_catalog.hh
@@ -84,8 +84,13 @@ class AssetCatalogService {
   /**
    * Duplicate the catalogs from \a other_service into this one. Does not rebuild the tree, this
    * needs to be done by the caller (call #rebuild_tree()!).
+   *
+   * \note If a catalog from \a other already exists in this collection (identified by catalog ID),
+   * it will be skipped and \a on_duplicate_items will be called.
    */
-  void add_from_existing(const AssetCatalogService &other_service);
+  void add_from_existing(const AssetCatalogService &other_service,
+                         FunctionRef<void(const AssetCatalog &existing,
+                                          const AssetCatalog &to_be_ignored)> on_duplicate_items);
 
   /**
    * Write the catalog definitions to disk.
@@ -298,11 +303,17 @@ class AssetCatalogCollection {
   AssetCatalogCollection(AssetCatalogCollection &&other) noexcept = default;
 
   std::unique_ptr<AssetCatalogCollection> deep_copy() const;
+  using OnDuplicateCatalogIdFn =
+      FunctionRef<void(const AssetCatalog &existing, const AssetCatalog &to_be_ignored)>;
   /**
    * Copy the catalogs from \a other and append them to this collection. Copies no other data
    * otherwise.
+   *
+   * \note If a catalog from \a other already exists in this collection (identified by catalog ID),
+   * it will be skipped and \a on_duplicate_items will be called.
    */
-  void add_catalogs_from_existing(const AssetCatalogCollection &other);
+  void add_catalogs_from_existing(const AssetCatalogCollection &other,
+                                  OnDuplicateCatalogIdFn on_duplicate_items);
 
  protected:
   static OwningAssetCatalogMap copy_catalog_map(const OwningAssetCatalogMap &orig);
diff --git a/source/blender/asset_system/intern/asset_catalog.cc b/source/blender/asset_system/intern/asset_catalog.cc
index 489ec4c227c..60547c1efca 100644
--- a/source/blender/asset_system/intern/asset_catalog.cc
+++ b/source/blender/asset_system/intern/asset_catalog.cc
@@ -344,9 +344,12 @@ void AssetCatalogService::load_from_disk(const CatalogFilePath &file_or_director
   this->rebuild_tree();
 }
 
-void AssetCatalogService::add_from_existing(const AssetCatalogService &other_service)
+void AssetCatalogService::add_from_existing(
+    const AssetCatalogService &other_service,
+    AssetCatalogCollection::OnDuplicateCatalogIdFn on_duplicate_items)
 {
-  catalog_collection_->add_catalogs_from_existing(*other_service.catalog_collection_);
+  catalog_collection_->add_catalogs_from_existing(*other_service.catalog_collection_,
+                                                  on_duplicate_items);
 }
 
 void AssetCatalogService::load_directory_recursive(const CatalogFilePath &directory_path)
@@ -692,24 +695,40 @@ std::unique_ptr<AssetCatalogCollection> AssetCatalogCollection::deep_copy() cons
   return copy;
 }
 
-static void copy_catalog_map_into_existing(const OwningAssetCatalogMap &source,
-                                           OwningAssetCatalogMap &dest)
+static void copy_catalog_map_into_existing(
+    const OwningAssetCatalogMap &source,
+    OwningAssetCatalogMap &dest,
+    AssetCatalogCollection::OnDuplicateCatalogIdFn on_duplicate_items)
 {
   for (const auto &orig_catalog_uptr : source.values()) {
+    if (dest.contains(orig_catalog_uptr->catalog_id)) {
+      if (on_duplicate_items) {
+        on_duplicate_items(*dest.lookup(orig_catalog_uptr->catalog_id), *orig_catalog_uptr);
+      }
+      continue;
+    }
+
     auto copy_catalog_uptr = std::make_unique<AssetCatalog>(*orig_catalog_uptr);
     dest.add_new(copy_catalog_uptr->catalog_id, std::move(copy_catalog_uptr));
   }
 }
 
-void AssetCatalogCollection::add_catalogs_from_existing(const AssetCatalogCollection &other)
+void AssetCatalogCollection::add_catalogs_from_existing(
+    const AssetCatalogCollection &other,
+    AssetCatalogCollection::OnDuplicateCatalogIdFn on_duplicate_items)
 {
-  copy_catalog_map_into_existing(other.catalogs_, catalogs_);
+  copy_catalog_map_into_existing(other.catalogs_, catalogs_, on_duplicate_items);
 }
 
 OwningAssetCatalogMap AssetCatalogCollection::copy_catalog_map(const OwningAssetCatalogMap &orig)
 {
   OwningAssetCatalogMap copy;
-  copy_catalog_map_into_existing(orig, copy);
+  copy_catalog_map_into_existing(
+      orig, copy, /*on_duplicate_items=*/[](const AssetCatalog &, const AssetCatalog &) {
+        /* `copy` was empty before. If this happens it means there was a duplicate in the `orig`
+         * catalog map which should've been caught already. */
+        BLI_assert_unreachable();
+      });
   return copy;
 }
 
diff --git a/source/blender/asset_system/intern/asset_library_all.cc b/source/blender/asset_system/intern/asset_library_all.cc
index ab927920dff..6c71417ffd4 100644
--- a/source/blender/asset_system/intern/asset_library_all.cc
+++ b/source/blender/asset_system/intern/asset_library_all.cc
@@ -12,6 +12,10 @@
 
 #include "asset_library_all.hh"
 
+#include "CLG_log.h"
+
+static CLG_LogRef LOG = {"asset_system.all_asset_library"};
+
 namespace blender::asset_system {
 
 AllAssetLibrary::AllAssetLibrary() : AssetLibrary(ASSET_LIBRARY_ALL) {}
@@ -28,9 +32,30 @@ void AllAssetLibrary::rebuild_catalogs_from_nested(const bool reload_nested_cata
         if (reload_nested_catalogs) {
           nested.catalog_service->reload_catalogs();
         }
-        new_catalog_service->add_from_existing(*nested.catalog_service);
+
+        new_catalog_service->add_from_existing(
+            *nested.catalog_service,
+            /*on_duplicate_items=*/[](const AssetCatalog &existing,
+                                      const AssetCatalog &to_be_ignored) {
+              if (existing.path == to_be_ignored.path) {
+                CLOG_INFO(&LOG,
+                          2,
+                          "multiple definitions of catalog %s (path: %s), ignoring duplicate",
+                          existing.catalog_id.str().c_str(),
+                          existing.path.c_str());
+              }
+              else {
+                CLOG_ERROR(&LOG,
+                           "multiple definitions of catalog %s with differing paths (%s vs. %s), "
+                           "ignoring second one",
+                           existing.catalog_id.str().c_str(),
+                           existing.path.c_str(),
+                           to_be_ignored.path.c_str());
+              }
+            });
       },
       false);
+
   new_catalog_service->rebuild_tree();
   this->catalog_service = std::move(new_catalog_service);
 }