The present study investigated cognitive function in children diagnosed with acute lymphoblastic leukemia (ALL). The subjects were 20 children between the ages of 6 and 12 years of both genders who were diagnosed with ALL and underwent exclusively triple intrathecal prophylactic chemotherapy of the central nervous system. The protocol used for the neuropsychological assessment included the following cognitive aspects: intellectual performance, attention, memory and executive function. Data were analyzed by descriptive and inferential statistics using the Mann-Whitney U test and Student t-test. The effects of gender, age at diagnosis, and time since the initiation of treatment on the children's performance were determined. The evaluation of intellectual performance revealed reduced scores in the group of children who were female and younger than 5 years of age at diagnosis, especially difficulty with verbal skills and working memory. With regard to attention systems, the different groups presented expected performance for their age. We observed lower scores in the different groups in executive function, aspects of the development of problem-solving strategies, self-regulation, cognitive flexibility and inhibitory control. Better performance was observed for episodic memory and semantic memory (immediate and recognition), but lower scores were found for learning and recall after interference. In conclusion, the present findings are both consistent and discordant with the literature in the field that alludes to the impact of chemotherapy on the maturation of the central nervous system.