diff --git a/sklearn/tree/_classes.py b/sklearn/tree/_classes.py
index dc08bee65d3d9..28f9b40ac095d 100644
--- a/sklearn/tree/_classes.py
+++ b/sklearn/tree/_classes.py
@@ -292,7 +292,7 @@ def _fit(
                     )
 
         # Determine output settings
-        n_samples, self.n_features_in_ = X.shape
+        n_samples, self.n_features_in_ = X.shape[0], X.shape[1]
 
         # Do preprocessing if 'y' is passed
         is_classification = False