The Tenggara swiftlet was described by the German ornithologist Erwin Stresemann in 1925 under the present binomial name Collocalia sumbawae.

[3][4] There are two subspecies:[4] The Tenggara swiftlet is 9–10 cm (3.5–3.9 in) in length with a square tail.

[5] The back and upper surface of the wings are dark blue with a moderate gloss.

The rump is generally dark but sometimes includes feathers with thin white edging.

There is occasionally a tuft of small feathers on the hallux, the rear facing toe.