Striated Swallow is 19 cm long with a deeply forked tail. It has blue upperparts other than a reddish collar (sometimes absent) and streaked chestnut rump. The face and underparts are white with heavy dark streaking. The wing are brown. The sexes are alike but juveniles are duller and browner, with a paler rump and shorter outer tail feathers.

There are five races

H. s. striolata breeds in Taiwan, The Philippines and Indonesia.
H. s. mayri breeds from northeastern India to northwestern Myanmar. It has broader streaks than nominate striolata.
H. s. stanfordi breeds from northeastern Myanmar to northern Thailand. It has broad streaks.
H. s. vernayi breeds locally in western Thailand. It is more rufous below than the nominate race, and is only faintly streaked on the rump.
H. s. badia breeds on the Malay Peninsula. It has faintly streaked deep rufous underparts, and an unstreaked rump. It is sometimes raised to species status as the Rufous-bellied Swallow, Hirundo badia or Cecropis badia.
The contact call is pin, the alarm is chi-chi-chi, and the song is a soft twittering.

This species, particularly subspecies mayri is very similar to Red-rumped Swallow of the race japonicus, but is larger, more heavily streaked, and has a less distinct neck collar.