All iPhone 6s Plus models have a 5.5" (diagonal) widescreen pressure-sensitive "3D Touch" LED-backlit 1920x1080 native resolution (401 ppi) "Retina HD" display with "IPS technology and a taptic engine," and dual cameras. The rear 12 megapixel, 4K "iSight" camera has 1.22 micron pixels, an f/2.2 aperture, support for simultaneous 4K video and 8 megapixel still photography, and optical image stabilization for both photos and video. The front 5 megapixel, 720p "FaceTime" camera is more modest in capability.

The iPhone 6s Plus uses a 7000 series aluminum housing and also packs a second generation "Touch ID" fingerprint sensor embedded in the "home" button.

The iPhone 6s Plus is powered by a 64-bit 1.8 GHz "Apple A9" processor and has 2 GB of LPDDR3 RAM. It also supports 802.11a/b/g/n/ac Wi-Fi with MIMO, Bluetooth 4.2, LTE (4G), and NFC for Apple Pay. It has a bottom-mounted headphone jack and uses a "Lightning" port to connect to a Mac, PC, dock, or power adapter.