The present study was the first to investigate the ability to selectively trust reliable informants in a sample of Brazilian preschool children from two different socioeconomic backgrounds. Ninety-three 3- and 4-year-old children, equally distributed across a low- and medium-SES group, participated. A standard selective trust task was used. Participants also completed the Scale of Theory-of Mind Tasks and a vocabulary test (PPVT). Children from the mid-SES group showed higher vocabulary and theory-of-mind scores, but surprisingly, their performance in the selective trust task was significantly worse than the low-SES group. No age effect was found, but results suggest a significant main effect of condition, with participants performing better when an accurate informant was pitted against a neutral informant in comparison to when an inaccurate informant was pitted against a neutral informant. This pattern of results contrasts with previous evidence with 3-year-old children in the U.S., who showed more selective performance in the presence of inaccurate informants. These findings are the first to demonstrate the influence of family SES on selective learning in childhood and point to promising lines of investigation on how mechanisms of selective trust may vary across socioeconomic contexts.