Avicularia hirschii is one of the smaller species of the genus. The male has instead of a tibia spur a lot of thick black spines similar to those of Avicularia versicolor (Walckenaer, 1837) from Martinique and Guadeloupe. Tufts of red hairs on the tarsi and the opisthosoma arranged in two rows framing the black middle section are typical. The length of the urticating hairs of type II is 0,10 - 0,17 mm. The embolus is long and tapered. The spermathecae are similar to those of A. azuraklaasi Tesmoingt, 1996 from Peru. Juvenile spiders are almost white coloured with black stripe on the opisthosoma. There is no Christmas tree pattern as in other Avicularia species.