The Magenta-throated Woodstar is a resident breeder in forest edge and scrub of the Talamancan montane forests. It is a tiny hummingbird with long tail that is often cocked up. Males are unmistakable with their magenta throat separated by a white collar from the green chest and flanks. Their back is green and belly is rufous. There are white rump patches, and the black-tipped tail is long and forked.
Females are generally like the males but their throat is gray-buff instead of magenta, and their tail sides are rufous. They lack the males' long tail. Immatures are like the females, but paler below and with buff fringes to the upperparts plumage.