diff --git a/src/mkdocs_bibtex/plugin.py b/src/mkdocs_bibtex/plugin.py
index 9733efa..b0cf826 100644
--- a/src/mkdocs_bibtex/plugin.py
+++ b/src/mkdocs_bibtex/plugin.py
@@ -66,7 +66,7 @@ def on_config(self, config):
             else:
                 bibfiles.append(self.config["bib_file"])
         elif self.config.get("bib_dir", None) is not None:
-            bibfiles.extend(Path(self.config["bib_dir"]).glob("*.bib"))
+            bibfiles.extend(Path(self.config["bib_dir"]).rglob("*.bib"))
         else:  # pragma: no cover
             raise Exception("Must supply a bibtex file or directory for bibtex files")
 
diff --git a/test_files/multi_bib/bib2.bib b/test_files/multi_bib/multi_bib_child_dir/bib2.bib
similarity index 100%
rename from test_files/multi_bib/bib2.bib
rename to test_files/multi_bib/multi_bib_child_dir/bib2.bib