Stigmella schinivora van Nieukerken, 2016 was described from Cataratas de Iguazu, Misiones, Argentina, based on adults reared from Schinus terebinthifolius Raddi (Anacardiaceae) leaf mines. The aim of this study is to describe for the first time the external morphology of the immature stages of S. schinivora with the aid of light and scanning electron microscopy, based on mines collected on the same host plant, but in Laranjeiras do Sul, Parana, Brazil. Data on natural history, including histology of the mines, are also provided. The larva passes through four instars, all endophytic, having chewing mouth parts and feeding on the palisade parenchyma. The first three instars are apodous and have a subcylindrical body, bearing only one pair of setae on the tenth abdominal segment; the fourth instar is eruciform, with well-developed ambulatory calli on thorax and abdomen and setae on all tagmata. A serpentine mine is constructed on the adaxial surface, progressively increasing in width during larval development. With the exception of the widened, terminal section, the mine is left filled with larval feces. The fully developed larva of last instar exits through a slit made at the distal end of the mine, building a silk cocoon on the leaf abaxial surface where pupation occurs. This is the first record of S. schinivora from Brazil, which was only known from the type locality in Argentina.