diff --git a/src/dotenv/main.py b/src/dotenv/main.py
index 3c4608d5..d7d4009d 100644
--- a/src/dotenv/main.py
+++ b/src/dotenv/main.py
@@ -216,7 +216,8 @@ def set_key(
     )
 
     if quote:
-        value_out = "'{}'".format(value_to_set.replace("'", "\\'"))
+        escaped_value = value_to_set.replace("\\", "\\\\").replace("'", "\\'")
+        value_out = f"'{escaped_value}'"
     else:
         value_out = value_to_set
     if export:
diff --git a/tests/test_main.py b/tests/test_main.py
index 1c33c808..ee357632 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -63,6 +63,21 @@ def test_set_key_encoding(dotenv_path):
     assert dotenv_path.read_text(encoding=encoding) == "a='é'\n"
 
 
+@pytest.mark.parametrize(
+    "value",
+    [
+        "C:\\Users\\name",
+        r"\\d+",
+        r"prefix\\suffix",
+        "backslash\\'quote",
+    ],
+)
+def test_set_key_round_trips_backslashes(dotenv_path, value):
+    dotenv.set_key(dotenv_path, "VALUE", value)
+
+    assert dotenv.get_key(dotenv_path, "VALUE") == value
+
+
 @pytest.mark.skipif(
     sys.platform == "win32", reason="file mode bits behave differently on Windows"
 )