Males measure between 21 and 24 centimeters long, including the long tail. They are mostly green, with long black tail feathers and an iridescent green patch on the chest and throat. Females are between 13.5 and 14.5 centimeters in length. They differ from the male in having a shorter tail and white underparts with green spots. The black-tailed trainbearer has a longer, more decurved bill and (in males) a longer, more curved tail than the green-tailed trainbearer, and also tends to be duller green overall. With a wing length of 59.9mm, Lesbia victoriae victoriae Is the largest subspecies in the genus Lesbia.