diff --git a/src/Dom/findDOMNode.ts b/src/Dom/findDOMNode.ts
index 288ec01a..0b90b9b8 100644
--- a/src/Dom/findDOMNode.ts
+++ b/src/Dom/findDOMNode.ts
@@ -1,9 +1,10 @@
-import React from 'react';
+import type React from 'react';
 
 export function isDOM(node: any): node is HTMLElement | SVGElement {
-  // https://developer.mozilla.org/en-US/docs/Web/API/Element
-  // Since XULElement is also subclass of Element, we only need HTMLElement and SVGElement
-  return node instanceof HTMLElement || node instanceof SVGElement;
+  // Cross-frame safe check: `instanceof` fails for elements created in a
+  // different frame (e.g. iframe via createPortal) because each frame has its
+  // own HTMLElement/SVGElement constructors.
+  return typeof node === 'object' && node !== null && node.nodeType === 1;
 }
 
 /**
diff --git a/src/Dom/isVisible.ts b/src/Dom/isVisible.ts
index 13dea10c..67badcef 100644
--- a/src/Dom/isVisible.ts
+++ b/src/Dom/isVisible.ts
@@ -3,7 +3,7 @@ export default (element: Element): boolean => {
     return false;
   }
 
-  if (element instanceof Element) {
+  if (element.nodeType === 1) {
     if ((element as HTMLElement).offsetParent) {
       return true;
     }
diff --git a/tests/findDOMNode.test.tsx b/tests/findDOMNode.test.tsx
index 0856b81a..973e7a76 100644
--- a/tests/findDOMNode.test.tsx
+++ b/tests/findDOMNode.test.tsx
@@ -63,6 +63,27 @@ describe('findDOMNode', () => {
     expect(findDOMNode(svg)).toBe(svg);
   });
 
+  it('supports DOM nodes from iframe', () => {
+    const iframe = document.createElement('iframe');
+    document.body.appendChild(iframe);
+
+    try {
+      const iframeWindow = iframe.contentWindow!;
+      const iframeDocument = iframeWindow.document;
+      const div = iframeDocument.createElement('div');
+      iframeDocument.body.appendChild(div);
+
+      expect(div).toBeInstanceOf(iframeWindow.HTMLElement);
+      expect(div).not.toBeInstanceOf(HTMLElement);
+      expect(isDOM(div)).toBe(true);
+      expect(getDOM(div)).toBe(div);
+      expect(findDOMNode(div)).toBe(div);
+      expect(getDOM({ nativeElement: div })).toBe(div);
+    } finally {
+      document.body.removeChild(iframe);
+    }
+  });
+
   it('isDOM type', () => {
     const svg: any = document.createElementNS(
       'http://www.w3.org/2000/svg',
diff --git a/tests/isVisible.test.ts b/tests/isVisible.test.ts
new file mode 100644
index 00000000..bb2d474d
--- /dev/null
+++ b/tests/isVisible.test.ts
@@ -0,0 +1,33 @@
+import isVisible from '../src/Dom/isVisible';
+
+describe('isVisible', () => {
+  it('supports DOM nodes from iframe', () => {
+    const iframe = document.createElement('iframe');
+    document.body.appendChild(iframe);
+
+    try {
+      const iframeWindow = iframe.contentWindow!;
+      const iframeDocument = iframeWindow.document;
+      const div = iframeDocument.createElement('div');
+      iframeDocument.body.appendChild(div);
+
+      jest.spyOn(div, 'getBoundingClientRect').mockReturnValue({
+        bottom: 10,
+        height: 10,
+        left: 0,
+        right: 10,
+        toJSON: () => {},
+        top: 0,
+        width: 10,
+        x: 0,
+        y: 0,
+      });
+
+      expect(div).toBeInstanceOf(iframeWindow.HTMLElement);
+      expect(div).not.toBeInstanceOf(Element);
+      expect(isVisible(div)).toBe(true);
+    } finally {
+      document.body.removeChild(iframe);
+    }
+  });
+});