Like the previous Seville, five occupants fit inside the STS, which has soft all-leather seats. Heated and ventilated seating is an option. The headliner and pillars are covered in woven fabric. Genuine eucalyptus wood and aluminum trim are used in the interior.

Eight-way power front seats include four-way power lumbar adjustment, and a memory feature is optional. A leather-wrapped heated steering wheel is also offered. Trunk space totals 13.8 cubic feet.

Options include a Bose Studio Surround Sound system with 15 speakers and 300-watt output. An optional in-dash DVD/CD changer can play DVD audio discs as well as MP3 programs. A DVD-based navigation system is available. GM's OnStar communication system includes automatic crash notification.