diff --git a/test/fixtures/wpt/README.md b/test/fixtures/wpt/README.md
index 52d4ccc8294a6c..9474d8a1963b7e 100644
--- a/test/fixtures/wpt/README.md
+++ b/test/fixtures/wpt/README.md
@@ -16,6 +16,7 @@ Last update:
 - encoding: https://github.com/web-platform-tests/wpt/tree/35f70910d3/encoding
 - FileAPI: https://github.com/web-platform-tests/wpt/tree/3b279420d4/FileAPI
 - hr-time: https://github.com/web-platform-tests/wpt/tree/9910784394/hr-time
+- html/webappapis/atob: https://github.com/web-platform-tests/wpt/tree/f267e1dca6/html/webappapis/atob
 - html/webappapis/microtask-queuing: https://github.com/web-platform-tests/wpt/tree/2c5c3c4c27/html/webappapis/microtask-queuing
 - html/webappapis/timers: https://github.com/web-platform-tests/wpt/tree/5873f2d8f1/html/webappapis/timers
 - interfaces: https://github.com/web-platform-tests/wpt/tree/79fa4cf76e/interfaces
diff --git a/test/fixtures/wpt/html/webappapis/atob/base64.any.js b/test/fixtures/wpt/html/webappapis/atob/base64.any.js
new file mode 100644
index 00000000000000..7f433f4d8a9ee2
--- /dev/null
+++ b/test/fixtures/wpt/html/webappapis/atob/base64.any.js
@@ -0,0 +1,163 @@
+/**
+ * btoa() as defined by the HTML5 spec, which mostly just references RFC4648.
+ */
+function mybtoa(s) {
+    // String conversion as required by WebIDL.
+    s = String(s);
+
+    // "The btoa() method must throw an INVALID_CHARACTER_ERR exception if the
+    // method's first argument contains any character whose code point is
+    // greater than U+00FF."
+    for (var i = 0; i < s.length; i++) {
+        if (s.charCodeAt(i) > 255) {
+            return "INVALID_CHARACTER_ERR";
+        }
+    }
+
+    var out = "";
+    for (var i = 0; i < s.length; i += 3) {
+        var groupsOfSix = [undefined, undefined, undefined, undefined];
+        groupsOfSix[0] = s.charCodeAt(i) >> 2;
+        groupsOfSix[1] = (s.charCodeAt(i) & 0x03) << 4;
+        if (s.length > i + 1) {
+            groupsOfSix[1] |= s.charCodeAt(i + 1) >> 4;
+            groupsOfSix[2] = (s.charCodeAt(i + 1) & 0x0f) << 2;
+        }
+        if (s.length > i + 2) {
+            groupsOfSix[2] |= s.charCodeAt(i + 2) >> 6;
+            groupsOfSix[3] = s.charCodeAt(i + 2) & 0x3f;
+        }
+        for (var j = 0; j < groupsOfSix.length; j++) {
+            if (typeof groupsOfSix[j] == "undefined") {
+                out += "=";
+            } else {
+                out += btoaLookup(groupsOfSix[j]);
+            }
+        }
+    }
+    return out;
+}
+
+/**
+ * Lookup table for mybtoa(), which converts a six-bit number into the
+ * corresponding ASCII character.
+ */
+function btoaLookup(idx) {
+    if (idx < 26) {
+        return String.fromCharCode(idx + 'A'.charCodeAt(0));
+    }
+    if (idx < 52) {
+        return String.fromCharCode(idx - 26 + 'a'.charCodeAt(0));
+    }
+    if (idx < 62) {
+        return String.fromCharCode(idx - 52 + '0'.charCodeAt(0));
+    }
+    if (idx == 62) {
+        return '+';
+    }
+    if (idx == 63) {
+        return '/';
+    }
+    // Throw INVALID_CHARACTER_ERR exception here -- won't be hit in the tests.
+}
+
+function btoaException(input) {
+    input = String(input);
+    for (var i = 0; i < input.length; i++) {
+        if (input.charCodeAt(i) > 255) {
+            return true;
+        }
+    }
+    return false;
+}
+
+function testBtoa(input) {
+    // "The btoa() method must throw an INVALID_CHARACTER_ERR exception if the
+    // method's first argument contains any character whose code point is
+    // greater than U+00FF."
+    var normalizedInput = String(input);
+    for (var i = 0; i < normalizedInput.length; i++) {
+        if (normalizedInput.charCodeAt(i) > 255) {
+            assert_throws_dom("InvalidCharacterError", function() { btoa(input); },
+                "Code unit " + i + " has value " + normalizedInput.charCodeAt(i) + ", which is greater than 255");
+            return;
+        }
+    }
+    assert_equals(btoa(input), mybtoa(input));
+    assert_equals(atob(btoa(input)), String(input), "atob(btoa(input)) must be the same as String(input)");
+}
+
+var tests = ["עברית", "", "ab", "abc", "abcd", "abcde",
+    // This one is thrown in because IE9 seems to fail atob(btoa()) on it.  Or
+    // possibly to fail btoa().  I actually can't tell what's happening here,
+    // but it doesn't hurt.
+    "\xff\xff\xc0",
+    // Is your DOM implementation binary-safe?
+    "\0a", "a\0b",
+    // WebIDL tests.
+    undefined, null, 7, 12, 1.5, true, false, NaN, +Infinity, -Infinity, 0, -0,
+    {toString: function() { return "foo" }},
+];
+for (var i = 0; i < 258; i++) {
+    tests.push(String.fromCharCode(i));
+}
+tests.push(String.fromCharCode(10000));
+tests.push(String.fromCharCode(65534));
+tests.push(String.fromCharCode(65535));
+
+// This is supposed to be U+10000.
+tests.push(String.fromCharCode(0xd800, 0xdc00));
+tests = tests.map(
+    function(elem) {
+        var expected = mybtoa(elem);
+        if (expected === "INVALID_CHARACTER_ERR") {
+            return ["btoa("  + format_value(elem) + ") must raise INVALID_CHARACTER_ERR", elem];
+        }
+        return ["btoa(" + format_value(elem) + ") == " + format_value(mybtoa(elem)), elem];
+    }
+);
+
+var everything = "";
+for (var i = 0; i < 256; i++) {
+    everything += String.fromCharCode(i);
+}
+tests.push(["btoa(first 256 code points concatenated)", everything]);
+
+generate_tests(testBtoa, tests);
+
+promise_test(() => fetch("../../../fetch/data-urls/resources/base64.json").then(res => res.json()).then(runAtobTests), "atob() setup.");
+
+const idlTests = [
+  [undefined, null],
+  [null, [158, 233, 101]],
+  [7, null],
+  [12, [215]],
+  [1.5, null],
+  [true, [182, 187]],
+  [false, null],
+  [NaN, [53, 163]],
+  [+Infinity, [34, 119, 226, 158, 43, 114]],
+  [-Infinity, null],
+  [0, null],
+  [-0, null],
+  [{toString: function() { return "foo" }}, [126, 138]],
+  [{toString: function() { return "abcd" }}, [105, 183, 29]]
+];
+
+function runAtobTests(tests) {
+  const allTests = tests.concat(idlTests);
+  for(let i = 0; i < allTests.length; i++) {
+    const input = allTests[i][0],
+          output = allTests[i][1];
+    test(() => {
+      if(output === null) {
+        assert_throws_dom("InvalidCharacterError", () => globalThis.atob(input));
+      } else {
+        const result = globalThis.atob(input);
+        for(let ii = 0; ii < output.length; ii++) {
+          assert_equals(result.charCodeAt(ii), output[ii]);
+        }
+      }
+    }, "atob(" + format_value(input) + ")");
+  }
+}
diff --git a/test/fixtures/wpt/versions.json b/test/fixtures/wpt/versions.json
index c533088b4693b8..800f07c607bf4b 100644
--- a/test/fixtures/wpt/versions.json
+++ b/test/fixtures/wpt/versions.json
@@ -23,6 +23,10 @@
     "commit": "9910784394858a8e34d9eb4e5d00788765abf837",
     "path": "hr-time"
   },
+  "html/webappapis/atob": {
+    "commit": "f267e1dca6f57a9f4d69f32a6920adfdb3268656",
+    "path": "html/webappapis/atob"
+  },
   "html/webappapis/microtask-queuing": {
     "commit": "2c5c3c4c27d27a419c1fdba3e9879c2d22037074",
     "path": "html/webappapis/microtask-queuing"
diff --git a/test/wpt/status/html/webappapis/atob.json b/test/wpt/status/html/webappapis/atob.json
new file mode 100644
index 00000000000000..65deda7312d426
--- /dev/null
+++ b/test/wpt/status/html/webappapis/atob.json
@@ -0,0 +1,5 @@
+{
+  "base64.any.js": {
+    "fail": "promise_test: Unhandled rejection with value: object \"Error: ENOENT: no such file or directory, open '/root/node/node/fetch/data-urls/resources/base64.json'\""
+  }
+}
diff --git a/test/wpt/test-atob.js b/test/wpt/test-atob.js
new file mode 100644
index 00000000000000..51fa27e36d3f2f
--- /dev/null
+++ b/test/wpt/test-atob.js
@@ -0,0 +1,19 @@
+'use strict';
+
+require('../common');
+const { WPTRunner } = require('../common/wpt');
+
+const runner = new WPTRunner('html/webappapis/atob');
+
+// Needed to access to DOMException.
+runner.setFlags(['--expose-internals']);
+
+// Set a script that will be executed in the worker before running the tests.
+runner.setInitScript(`
+  const { internalBinding } = require('internal/test/binding');
+  const { atob, btoa } = require('buffer');
+  const { DOMException } = internalBinding('messaging');
+  global.DOMException = DOMException;
+`);
+
+runner.runJsTests();