diff --git a/data_structures/binary_search_tree.ts b/data_structures/binary_search_tree.ts
index 4fa0e2b75475..4ac1c352538a 100644
--- a/data_structures/binary_search_tree.ts
+++ b/data_structures/binary_search_tree.ts
@@ -281,6 +281,7 @@ export class BinarySearchTree<T> implements Iterable<T> {
             nodes.push(right);
           }
         }
+        result.#size = collection.#size;
       }
     } else {
       result = (options?.compare
diff --git a/data_structures/binary_search_tree_test.ts b/data_structures/binary_search_tree_test.ts
index 3d5f80c4e0ec..c587dd26a617 100644
--- a/data_structures/binary_search_tree_test.ts
+++ b/data_structures/binary_search_tree_test.ts
@@ -392,6 +392,7 @@ Deno.test("BinarySearchTree.from() handles default ascend comparator", () => {
   let tree: BinarySearchTree<number> = BinarySearchTree.from(originalTree);
   assertEquals([...originalTree], expected);
   assertEquals([...tree], expected);
+  assertEquals(tree.size, originalTree.size);
   assertEquals([...tree.nlrValues()], [...originalTree.nlrValues()]);
   assertEquals([...tree.lvlValues()], [...originalTree.lvlValues()]);
 
@@ -443,6 +444,7 @@ Deno.test("BinarySearchTree.from() handles descend comparator", () => {
   let tree: BinarySearchTree<number> = BinarySearchTree.from(originalTree);
   assertEquals([...originalTree], expected);
   assertEquals([...tree], expected);
+  assertEquals(tree.size, originalTree.size);
   assertEquals([...tree.nlrValues()], [...originalTree.nlrValues()]);
   assertEquals([...tree.lvlValues()], [...originalTree.lvlValues()]);