diff --git a/doc/api/stream.md b/doc/api/stream.md
index 1e87af4d8f6677..a4f8ed6e5aedab 100644
--- a/doc/api/stream.md
+++ b/doc/api/stream.md
@@ -2579,6 +2579,9 @@ further errors except from `_destroy()` may be emitted as `'error'`.
 <!-- YAML
 added: v10.0.0
 changes:
+  - version: v18.14.0
+    pr-url: https://github.com/nodejs/node/pull/46205
+    description: Added support for `ReadableStream` and `WritableStream`.
   - version: v15.11.0
     pr-url: https://github.com/nodejs/node/pull/37354
     description: The `signal` option was added.
@@ -2598,7 +2601,9 @@ changes:
                  finished before the call to `finished(stream, cb)`.
 -->
 
-* `stream` {Stream} A readable and/or writable stream.
+* `stream` {Stream|ReadableStream|WritableStream}
+
+A readable and/or writable stream/webstream.
 
 * `options` {Object}
   * `error` {boolean} If set to `false`, then a call to `emit('error', err)` is
@@ -3022,10 +3027,16 @@ added: v17.0.0
 
 <!-- YAML
 added: v16.8.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/46190
+    description: The `src` argument can now be a `ReadableStream` or
+                 `WritableStream`.
 -->
 
 * `src` {Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable|
-  AsyncGeneratorFunction|AsyncFunction|Promise|Object}
+  AsyncGeneratorFunction|AsyncFunction|Promise|Object|
+  ReadableStream|WritableStream}
 
 A utility method for creating duplex streams.
 
@@ -3045,6 +3056,8 @@ A utility method for creating duplex streams.
   `writable` into `Stream` and then combines them into `Duplex` where the
   `Duplex` will write to the `writable` and read from the `readable`.
 * `Promise` converts into readable `Duplex`. Value `null` is ignored.
+* `ReadableStream` converts into readable `Duplex`.
+* `WritableStream` converts into writable `Duplex`.
 * Returns: {stream.Duplex}
 
 If an `Iterable` object containing promises is passed as an argument,
diff --git a/lib/internal/streams/duplexify.js b/lib/internal/streams/duplexify.js
index 13404e43bf1bae..788bcb63242c38 100644
--- a/lib/internal/streams/duplexify.js
+++ b/lib/internal/streams/duplexify.js
@@ -8,6 +8,8 @@ const {
   isReadableNodeStream,
   isWritableNodeStream,
   isDuplexNodeStream,
+  isReadableStream,
+  isWritableStream,
 } = require('internal/streams/utils');
 const eos = require('internal/streams/end-of-stream');
 const {
@@ -20,6 +22,7 @@ const {
 const { destroyer } = require('internal/streams/destroy');
 const Duplex = require('internal/streams/duplex');
 const Readable = require('internal/streams/readable');
+const Writable = require('internal/streams/writable');
 const { createDeferredPromise } = require('internal/util');
 const from = require('internal/streams/from');
 
@@ -71,15 +74,13 @@ module.exports = function duplexify(body, name) {
     return _duplexify({ writable: false, readable: false });
   }
 
-  // TODO: Webstreams
-  // if (isReadableStream(body)) {
-  //   return _duplexify({ readable: Readable.fromWeb(body) });
-  // }
+  if (isReadableStream(body)) {
+    return _duplexify({ readable: Readable.fromWeb(body) });
+  }
 
-  // TODO: Webstreams
-  // if (isWritableStream(body)) {
-  //   return _duplexify({ writable: Writable.fromWeb(body) });
-  // }
+  if (isWritableStream(body)) {
+    return _duplexify({ writable: Writable.fromWeb(body) });
+  }
 
   if (typeof body === 'function') {
     const { value, write, final, destroy } = fromAsyncGen(body);
@@ -146,13 +147,12 @@ module.exports = function duplexify(body, name) {
     });
   }
 
-  // TODO: Webstreams.
-  // if (
-  //   isReadableStream(body?.readable) &&
-  //   isWritableStream(body?.writable)
-  // ) {
-  //   return Duplexify.fromWeb(body);
-  // }
+  if (
+    isReadableStream(body?.readable) &&
+    isWritableStream(body?.writable)
+  ) {
+    return Duplexify.fromWeb(body);
+  }
 
   if (
     typeof body?.writable === 'object' ||
diff --git a/test/parallel/test-stream-duplex-from.js b/test/parallel/test-stream-duplex-from.js
index c3f3dd756b2e66..e3c117ff8dedb0 100644
--- a/test/parallel/test-stream-duplex-from.js
+++ b/test/parallel/test-stream-duplex-from.js
@@ -3,6 +3,7 @@
 const common = require('../common');
 const assert = require('assert');
 const { Duplex, Readable, Writable, pipeline, PassThrough } = require('stream');
+const { ReadableStream, WritableStream } = require('stream/web');
 const { Blob } = require('buffer');
 
 {
@@ -299,3 +300,104 @@ const { Blob } = require('buffer');
     assert.strictEqual(res, 'foobar');
   })).on('close', common.mustCall());
 }
+
+function makeATestReadableStream(value) {
+  return new ReadableStream({
+    start(controller) {
+      controller.enqueue(value);
+      controller.close();
+    }
+  });
+}
+
+function makeATestWritableStream(writeFunc) {
+  return new WritableStream({
+    write(chunk) {
+      writeFunc(chunk);
+    }
+  });
+}
+
+{
+  const d = Duplex.from({
+    readable: makeATestReadableStream('foo'),
+  });
+  assert.strictEqual(d.readable, true);
+  assert.strictEqual(d.writable, false);
+
+  d.on('data', common.mustCall((data) => {
+    assert.strictEqual(data.toString(), 'foo');
+  }));
+
+  d.on('end', common.mustCall(() => {
+    assert.strictEqual(d.readable, false);
+  }));
+}
+
+{
+  const d = Duplex.from(makeATestReadableStream('foo'));
+
+  assert.strictEqual(d.readable, true);
+  assert.strictEqual(d.writable, false);
+
+  d.on('data', common.mustCall((data) => {
+    assert.strictEqual(data.toString(), 'foo');
+  }));
+
+  d.on('end', common.mustCall(() => {
+    assert.strictEqual(d.readable, false);
+  }));
+}
+
+{
+  let ret = '';
+  const d = Duplex.from({
+    writable: makeATestWritableStream((chunk) => ret += chunk),
+  });
+
+  assert.strictEqual(d.readable, false);
+  assert.strictEqual(d.writable, true);
+
+  d.end('foo');
+  d.on('finish', common.mustCall(() => {
+    assert.strictEqual(ret, 'foo');
+    assert.strictEqual(d.writable, false);
+  }));
+}
+
+{
+  let ret = '';
+  const d = Duplex.from(makeATestWritableStream((chunk) => ret += chunk));
+
+  assert.strictEqual(d.readable, false);
+  assert.strictEqual(d.writable, true);
+
+  d.end('foo');
+  d.on('finish', common.mustCall(() => {
+    assert.strictEqual(ret, 'foo');
+    assert.strictEqual(d.writable, false);
+  }));
+}
+
+{
+  let ret = '';
+  const d = Duplex.from({
+    readable: makeATestReadableStream('foo'),
+    writable: makeATestWritableStream((chunk) => ret += chunk),
+  });
+
+  d.end('bar');
+
+  d.on('data', common.mustCall((data) => {
+    assert.strictEqual(data.toString(), 'foo');
+  }));
+
+  d.on('end', common.mustCall(() => {
+    assert.strictEqual(d.readable, false);
+  }));
+
+  d.on('finish', common.mustCall(() => {
+    assert.strictEqual(ret, 'bar');
+    assert.strictEqual(d.writable, false);
+  }));
+}