The iPhone Duo is compatible with the Apple Pencil, but only the USB-C model. Older Apple Pencils (1, 2, or Pro) will not work with the device. To pair the USB-C Apple Pencil with the iPhone Duo, a USB-C cable is required, unlike the magnetic pairing of the Pro model with iPads. Apple Pencil support is being integrated with iOS 27.2, currently in beta. Once paired, the Apple Pencil functions similarly to its use on an iPad, allowing for writing and drawing with palm rejection. It can be used on both the inner and outer displays of the iPhone Duo. While the Apple Pencil can magnetically attach to the Duo's hinge for storage, it does not charge in this manner. The USB-C Apple Pencil lacks advanced features found in the Pro model, such as pressure sensitivity, double-tap, and squeeze. Although the Apple Pencil tip may leave temporary marks on the Duo's display, these can be wiped away, and a screen replacement option is available if needed. For note-taking or sketching, the USB-C Apple Pencil offers some utility, though its usefulness is diminished compared to an iPad due to the iPhone Duo's smaller screen size.