We evaluated the effects of TutorBright tutoring on the reading and mathematics skills of children in family foster care, examined several potential moderators of the impact of tutoring, and explored possible 'spill-over' effects on the children's executive functioning and behavioural difficulties and on their caregivers' level of involvement in schoolwork in the home. The sample consisted of 70 children in care in Ontario, Canada. At the pre-test, the children were aged 5-16 years (M = 10.41, SD = 2.94) and enrolled in school grades 1-11 (M = 5.53, SD = 2.90). Thirty-four children were randomly assigned to tutoring and 36 to a waiting list control condition. Seven subtests from the Woodcock-Johnson III (WJ-III) achievement test served as outcome measures. The tutored children made statistically greater gains than those in the control group on the WJ-III subtests of Reading Fluency, Reading Comprehension, and Mathematics Calculation, but not on Word Reading, Spelling, Math Fluency, or Applied Math Problems. Age, executive functioning, caregiver controlling involvement in schoolwork, and self-reported post-traumatic stress disorder symptoms were found to moderate the effectiveness of tutoring. There were no spill-over effects of tutoring. The implications of the results for improving foster children's reading and mathematics skills were discussed.