All iPhone 6s Plus models have a 5.5 (diagonal) widescreen pressure-sensitive 3D Touch LED-backlit 1920×1080 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 is available in four metallic color options — silver, which has a white glass front and a silver colored back; gold, which has a white glass front and a gold colored back; space gray, which has a black glass front and a medium toned gray back; and rose gold, which has a white glass front and a pink-tinted gold colored back (pictured). It also packs a second generation Touch ID fingerprint sensor embedded in the home button.

The iPhone 6s Plus is powered by a 64-bit 1.85 GHz Apple A9 processor and has 2 GB of LPDDR3 RAM and 16 GB, 32 GB, 64 GB, or 128 GB of flash storage (16 GB and 64 GB options discontinued and 32 GB option introduced on September 7, 2016). 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.

Apple estimates that the iPhone 6s Plus provides up to 80 hours of audio playback, 12 hours of talk time on 3G, 12 hours of Internet use on 3G, 12 hours of Internet use on LTE, 12 hours of Internet use on Wi-Fi, 14 hours of video playback and up to 16 days of standby time.