One of the Matrix's unique design features is its interior, particularly the rear 60/40 seats and cargo area. Made with rigid plastic backs, the rear seats fold flat, creating a 53.2 cu ft (1.51 m3) cargo area. In a practicality test, however, Motor Trend was able to haul more cargo in the Matrix than in a Subaru WRX wagon with 61.1 cu ft (1.73 m3) of space.
In addition to the eight tie-downs in the back for attaching the included cargo nets and tonneau cover, the seats and rear floor have integrated rails for installing extra tie-downs.