The car, characterised by its "wedge" shape and by a swage line sweeping down from the rear to just behind the front wheel, was commonly advertised as "the shape of things to come". The design was penned by Harris Mann who also designed the wedge-shaped Princess. The car has an overall length of 160 in (410 cm), width of 66 in (170 cm), wheelbase of 85 in (220 cm) and height of 49.5 in (126 cm). The coupé has a kerbside weight of 2,205 lb (1,000 kg). During development, the TR7 was referred to by the code name "Bullet".[5] MGbranding was considered for the upmarket versions compared to the TR badged entry level versions, with "MG Magna" being used on some of the early clay models, but this did not reach production.[5][6]

The TR7 was the first of Triumph's 'TR' line to not be offered as a convertible in its initial form, instead utilizing a 2-door coupé configuration. With the United States showing increased concern for automotive safety in the 1970s, legislations were being considered to ban open roof convertibles in said markets due to rollover risks.[7] As the US statistically represented the most lucrative market for Triumph sports cars, it was decided that the TR7 would avoid these potential risks by only being offered as a fixed roof coupé. The legislations for the ban of convertibles ended up not being implemented however, and thus Triumph would later offer a convertible version of the TR7 beginning in 1979.