The Mexican fireleg resembles its better-known relative, the Mexican redknee tarantula (Brachypelma hamorii, formerly confused with Brachypelma smithi), in its dramatic orange and black coloration,though the adults of the species range from 5 to 6 inches in size.
This species of tarantula has a slower growth rate than many of the larger South American tarantula species. The black femora (upper legs) provide a dark dividing band between the rich orange color of the carapace and lower legs.
Unlike the orange joints of Brachypelma hamorii, the legs of this species are a bright, fiery red on the patellae (or knees), fading gradually to a paler orange further down and tipped by black tarsi (or feet). Although not particularly defensive, this species of spider can have a nervous temperament, where the spider can flick urticating hairs when it feels threatened.