diff --git a/CHANGELOG.md b/CHANGELOG.md
index d94812f6efad..2fc18fb8af4e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -87,6 +87,8 @@
   ([#5914](https://github.com/facebook/jest/pull/5914))
 * `[jest-regex-util]` Fix handling regex symbols in tests path on Windows
   ([#5941](https://github.com/facebook/jest/pull/5941))
+* `[jest-util]` Fix handling of NaN/Infinity in mock timer delay
+  ([#5966](https://github.com/facebook/jest/pull/5966))
 * `[jest-resolve]` Generalise test for package main entries equivalent to ".".
   ([#5968)](https://github.com/facebook/jest/pull/5968)
 
diff --git a/packages/jest-util/src/__tests__/fake_timers.test.js b/packages/jest-util/src/__tests__/fake_timers.test.js
index b59e0e00be3f..ac75ddf5ed01 100644
--- a/packages/jest-util/src/__tests__/fake_timers.test.js
+++ b/packages/jest-util/src/__tests__/fake_timers.test.js
@@ -315,17 +315,28 @@ describe('FakeTimers', () => {
       const mock2 = jest.fn(() => runOrder.push('mock2'));
       const mock3 = jest.fn(() => runOrder.push('mock3'));
       const mock4 = jest.fn(() => runOrder.push('mock4'));
+      const mock5 = jest.fn(() => runOrder.push('mock5'));
+      const mock6 = jest.fn(() => runOrder.push('mock6'));
 
       global.setTimeout(mock1, 100);
-      global.setTimeout(mock2, 0);
+      global.setTimeout(mock2, NaN);
       global.setTimeout(mock3, 0);
       const intervalHandler = global.setInterval(() => {
         mock4();
         global.clearInterval(intervalHandler);
       }, 200);
+      global.setTimeout(mock5, Infinity);
+      global.setTimeout(mock6, -Infinity);
 
       timers.runAllTimers();
-      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4']);
+      expect(runOrder).toEqual([
+        'mock2',
+        'mock3',
+        'mock5',
+        'mock6',
+        'mock1',
+        'mock4',
+      ]);
     });
 
     it('warns when trying to advance timers while real timers are used', () => {
diff --git a/packages/jest-util/src/fake_timers.js b/packages/jest-util/src/fake_timers.js
index 0633a3fa0640..f0064e66f744 100644
--- a/packages/jest-util/src/fake_timers.js
+++ b/packages/jest-util/src/fake_timers.js
@@ -486,9 +486,7 @@ export default class FakeTimers<TimerRef> {
       return null;
     }
 
-    if (delay == null) {
-      delay = 0;
-    }
+    delay = Number(delay) | 0;
 
     const args = [];
     for (let ii = 2, ll = arguments.length; ii < ll; ii++) {