diff --git a/.ci_support/environment.yml b/.ci_support/environment.yml
index 5224c6701..356dfeb38 100644
--- a/.ci_support/environment.yml
+++ b/.ci_support/environment.yml
@@ -10,7 +10,7 @@ dependencies:
 - nglview =4.0.1
 - notebook
 - numpy =2.4.3
-- phonopy =3.3.0
+- phonopy =3.4.0
 - plotly =6.6.0
 - pymatgen =2026.3.23
 - pyscal3 =3.3.2
diff --git a/pyproject.toml b/pyproject.toml
index 6c9b246a7..f8dd6aaab 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -52,7 +52,7 @@ surface = [
     "pymatgen==2026.3.23",
 ]
 phonopy = [
-    "phonopy==3.3.0",
+    "phonopy==3.4.0",
     "spglib==2.7.0",
 ]