Boiga trigonata has anterior palatine and mandibular teeth scarcely larger than the posterior.

The species has two postoculars, temporals 2+3, and 8 upper labials, with the third, fourth, and fifth entering the eye.

B. trigonata's body is moderately laterally compressed with smooth dorsal scales in 21 (or rarely 19) rows, with apical pits, disposed obliquely, with the vertebrals very feebly enlarged.

The race melanocephala is found in Pakistan; this form is variously considered as a subspecies, color variant, or full species.

Boiga trigonata strongly resembles venomous Echis carinatus in coloration and shape.