Reading difficulties of children growing up in poverty contexts have not received as much attention as those of children from middle-income families. This paper analyzes the reading-related cognitive profiles of Argentine, Spanish-speaking, low-SES children with reading difficulties (RD), by comparing them with chronological age- (CA) and reading age- (RA) matched children from the same socioeconomic background. Ninety children (30 in each group) participated in the study. Testing included reading, spelling, verbal memory, phonological sensitivity, rapid naming, letter knowledge, and vocabulary measures. Results showed that children from the RD group performed significantly worse than their same-age peers. These findings would suggest the presence of a cognitive vulnerability in children with reading difficulties. Interestingly, when compared with children from the RA-matched control group, children in the RD group only obtained significantly lower scores in phoneme segmentation and letter-sound recognition tasks. Cognitive profiles of low-income children growing in poverty differ from cognitive profiles described for middle-income children with dyslexia. Given that teaching of letter sounds is not included in Argentina's mandatory curriculum, it is possible that letter-sound teaching constitutes an environmental factor that interacts with other risk factors to produce reading difficulties in poverty contexts.