iPhone Duo owners looking to write or sketch with an Apple Pencil need the USB-C version of the accessory. Apple’s current instructions explicitly exclude other Pencil models. An Apple Pencil Pro you already use with an iPad is therefore not the right accessory for this phone.
The Verge reports that Pencil support arrived with iOS 27.2. The practical distinction is the exact model name, rather than whether a stylus carries Apple branding. Before buying anything, check which Pencil you own and whether the supported writing tools match what you want to do.
Pair with a cable, then disconnect
The model-specific setup guide says Apple Pencil (USB-C) is sold separately and is the compatible model. Pairing starts by sliding open the Pencil’s end, connecting it to a USB-C charge cable, then connecting the cable’s other end to the Duo. Tap “Tap to Connect” when prompted.
You can remove the cable after pairing. The Pencil also charges while connected to the phone, or through a USB-C power adapter. Its battery level is available in the Batteries widget or under Settings → Apple Pencil.
There is a useful caveat for anyone sharing a Pencil between devices: Apple says you must pair again after restarting the Duo, turning Bluetooth off, or pairing the Pencil with another device. Keep that procedure in mind before treating a lost connection as a fault. Moving an accessory back and forth may involve another cable connection.
Start with the writing task you need
The separate drawing and handwriting guide covers sketching in Notes and Freeform, marking up screenshots and documents, and writing in text fields with Scribble. Depending on the drawing tool, tilting the Pencil can change shading or line thickness.
Scribble converts handwriting into typed text. Apple also documents gestures for editing it, including scratching out a word to delete it and circling or underlining text to select it. You can enable Scribble and try its practice tool in Apple Pencil settings.
Try the specific job you have in mind, such as annotating a document or taking a handwritten note, using the supported model. Compatibility tells you which accessory can connect; it does not tell you whether handwriting on this phone will suit your routine better than typing.