diff --git a/src/my_project/interviews/top_150_questions_round_20/maximum_depth_tree.py b/src/my_project/interviews/top_150_questions_round_20/maximum_depth_tree.py
new file mode 100644
index 00000000..5d269794
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_20/maximum_depth_tree.py
@@ -0,0 +1,16 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+
+        if not root:
+            return 0
+        else: 
+            return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1
\ No newline at end of file
diff --git a/tests/test_150_questions_round_20/test_maximum_depth_tree_round_20.py b/tests/test_150_questions_round_20/test_maximum_depth_tree_round_20.py
new file mode 100644
index 00000000..d9903b57
--- /dev/null
+++ b/tests/test_150_questions_round_20/test_maximum_depth_tree_round_20.py
@@ -0,0 +1,19 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_20\
+.maximum_depth_tree import Solution, TreeNode
+
+class MaxDepthTreeTestCase(unittest.TestCase):
+
+    def test_max_depth_null(self):
+        solution = Solution()
+        tree = None
+        output = solution.maxDepth(root=tree)
+        target = 0
+        self.assertEqual(output, target)
+
+    def test_max_depth(self):
+        solution = Solution()
+        tree = TreeNode(1)
+        output = solution.maxDepth(root=tree)
+        target = 1
+        self.assertEqual(output, target)
\ No newline at end of file