diff --git a/data_structures/binary_tree/transform_bst_sum_tree.py b/data_structures/binary_tree/transform_bst_sum_tree.py
new file mode 100644
index 000000000000..49089313aec9
--- /dev/null
+++ b/data_structures/binary_tree/transform_bst_sum_tree.py
@@ -0,0 +1,138 @@
+from __future__ import annotations
+
+
+class Node:
+    def __init__(self, number: int) -> None:
+        self.data = number
+        self.left = None
+        self.right = None
+
+
+class BinaryTree:
+    def __init__(self, root=None) -> None:
+        self.root = root
+
+    def __iter__(self) -> int:
+        """
+        Test Case for BinaryTree's __iter__ method:
+
+        >>> tree = BinaryTree()
+        >>> root = tree.build_a_tree()
+        >>> list(tree)  # Get a list of values using __iter__
+        [1, 2, 7, 11, 15, 29, 35, 40]
+        """
+        if self.root is not None:
+            yield from self._traverse_inorder(self.root)
+
+    def __str__(self) -> str:
+        """
+        Returns a string representation of the inorder traversal of the binary tree.
+
+        Example:
+        >>> tree = BinaryTree()
+        >>> root = tree.build_a_tree()
+        >>> str(tree)
+        '1 2 7 11 15 29 35 40'
+        """
+        return " ".join(str(data) for data in self)
+
+    def _traverse_inorder(self, node: Node) -> int:
+        """
+        Test Case for BinaryTree's _traverse_inorder method:
+
+        >>> tree = BinaryTree()
+        >>> root = tree.build_a_tree()
+
+        # Inorder traversal of the tree should yield nodes in ascending order.
+        >>> list(tree._traverse_inorder(root))
+        [1, 2, 7, 11, 15, 29, 35, 40]
+        """
+        if node is not None:
+            yield from self._traverse_inorder(node.left)
+            yield node.data
+            yield from self._traverse_inorder(node.right)
+
+    def build_a_tree(self) -> Node:
+        # Create a binary tree with the specified structure
+        self.root = Node(11)
+        self.root.left = Node(2)
+        self.root.right = Node(29)
+        self.root.left.left = Node(1)
+        self.root.left.right = Node(7)
+        self.root.right.left = Node(15)
+        self.root.right.right = Node(40)
+        self.root.right.right.left = Node(35)
+        return self.root
+
+
+def transform_tree_util(root: Node | None) -> None:
+    """
+      Test Case for binary_tree_to_sum_tree:
+    >>>  tree = BinaryTree()
+    >>>  root = tree.build_a_tree()
+        # Transform the given binary tree into a sum tree
+    >>> binary_tree_to_sum_tree(root)
+
+
+    >>> root.data
+    139
+    >>> root.left.data
+    31
+    >>> root.right.data
+    75
+    >>> root.left.left.data
+    1
+    >>> root.left.right.data
+    7
+    >>> root.right.left.data
+    15
+    >>> root.right.right.data
+    40
+    >>> root.right.right.left.data
+    35
+    """
+    if root is None:
+        return
+
+    # Recur for right subtree
+    transform_tree_util(root.right)
+
+    # Update sum
+    global total
+    total = total + root.data
+
+    # Store old sum in the current node
+    root.data = total - root.data
+
+    # Recur for left subtree
+    transform_tree_util(root.left)
+
+
+def binary_tree_to_sum_tree(root: Node | None) -> None:
+    # Call the utility function to transform the tree
+    transform_tree_util(root)
+
+
+if __name__ == "__main__":
+    total = 0
+    tree = BinaryTree()
+    root = tree.build_a_tree()
+    # Transform the tree
+    binary_tree_to_sum_tree(root)
+    print("Transformed Tree:")
+    print(tree)
+
+    """
+    Test Cases:
+
+    >>> root = Node(11)
+    >>> root.left = Node(2)
+    >>> root.right = Node(29)
+    >>> transform_tree(root)
+    >>> root.data
+    60
+    >>> root.left.data
+    31
+    >>> root.right.data
+    29
+    """