--- a/browser/components/resistfingerprinting/test/browser/browser.ini
+++ b/browser/components/resistfingerprinting/test/browser/browser.ini
@@ -1,13 +1,14 @@
 [DEFAULT]
 tags = resistfingerprinting
 support-files =
   file_dummy.html
   head.js
 
+[browser_roundedWindow_dialogWindow.js]
 [browser_roundedWindow_newWindow.js]
 [browser_roundedWindow_open_max.js]
 [browser_roundedWindow_open_mid.js]
 [browser_roundedWindow_open_min.js]
 [browser_roundedWindow_windowSetting_max.js]
 [browser_roundedWindow_windowSetting_mid.js]
 [browser_roundedWindow_windowSetting_min.js]

new file mode 100644
--- /dev/null
+++ b/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_dialogWindow.js
@@ -0,0 +1,40 @@
+/**
+ * Bug 1352305 - A test case for dialog windows that it should not be rounded
+ *   even after fingerprinting resistance is enabled.
+ */
+
+async function test_dialog_window() {
+  let diagWin;
+
+  await new Promise(resolve => {
+    // Open a dialog window which is not rounded size.
+    diagWin = window.openDialog("about:blank", null,
+                                "innerWidth=250,innerHeight=350");
+
+    diagWin.addEventListener("load", function() {
+      resolve();
+    }, {once: true});
+  });
+
+  is(diagWin.innerWidth, 250, "The dialog window doesn't have a rounded size.");
+  is(diagWin.innerHeight, 350, "The dialog window doesn't have a rounded size.");
+
+  await BrowserTestUtils.closeWindow(diagWin);
+}
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({"set":
+    [["privacy.resistFingerprinting", true]]
+  });
+});
+
+add_task(test_dialog_window);
+
+add_task(async function test_dialog_window_without_resistFingerprinting() {
+  // Test dialog windows with 'privacy.resistFingerprinting' is false.
+  await SpecialPowers.pushPrefEnv({"set":
+    [["privacy.resistFingerprinting", false]]
+  });
+
+  await test_dialog_window();
+});