OBJECTIVE: To investigate the acute efficacy and adverse side effects of methylphenidate (MPH) among survivors of childhood cancer [acute lymphoblastic leukemia (ALL) or brain tumor (BT)] with learning impairments. METHODS: Participants (N = 122) completed a two-day, in-clinic, double-blind, cross-over trial during which they received MPH (0.60 mg/kg of body weight) and placebo that were randomized in administration order across participants. Performance was evaluated using measures of attention, memory, and academic achievement. RESULTS: A significant MPH versus placebo effect was revealed on a measure of attention, cognitive flexibility, and processing speed (Stroop Word-Color Association Test). Male gender, older age at treatment, and higher intelligence were predictive of better medication response. No significant differences were found for number or severity of adverse side effects as a function of active medication. CONCLUSIONS: MPH shows some neurocognitive benefit and is well tolerated by the majority of children surviving ALL and BT.