diff --git a/add-binary-string.py b/add-binary-string.py
new file mode 100644
index 000000000..4261cdb78
--- /dev/null
+++ b/add-binary-string.py
@@ -0,0 +1,29 @@
+# This function takes in two binary strings and returns their sum as a binary string
+
+def addBinary(a, b):
+    result = ""
+    i = len(a) - 1
+    j = len(b) - 1
+
+    carry = 0
+    while i >= 0 or j >= 0:
+        sum = carry
+        if i >= 0:
+            sum += ord(a[i]) - ord('0')
+        if j >= 0:
+
+            sum += ord(b[j]) - ord('0')
+        i = i - 1
+        j = j - 1
+        carry = 1 if sum > 1 else 0
+        result += str(sum % 2)
+
+    if carry != 0:
+        result += str(carry)
+    return result[::-1]
+
+
+if __name__ == '__main__':
+    print(addBinary("11", "1"))
+    print(addBinary("1010", "1011"))
+