Naupactus hirtellus is similar to Naupactus verecundus in color pattern and general body size. The vestiture is composed by iridescent green round scales, dense on the even intervals of elytra and sparse on the uneven intervals, especially along suture; elytral setae are stiff, slightly shorter than in Naupactus verecundus and dark towards apex. The pronotum is less rugose than in the latter species, the side are slightly curved and divergent towards base; the base of the elytra is slightly bisinuate; the front tibiae have very small denticles on the inner margin; and the corbels of hind tibiae are broad, squamose.
Males are more slender than females.
It causes damage on Gossypium hirsutum L. (Malvaceae). It is mainly associated with the native vegetation of the Chacoan biogeographic province.