diff --git a/pyproject.toml b/pyproject.toml
index e5584b581..67b13350b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,7 @@ classifiers = [
 dependencies = [
     "h5py>=2.10",
     "jsonschema>=2.6.0",
-    "numpy>=1.18",
+    'numpy>=1.18, <2.0', # pin below 2.0 until HDMF supports numpy 2.0
     "pandas>=1.0.5",
     "ruamel.yaml>=0.16",
     "scipy>=1.4",