Purpose: This study aimed to determine whether two aspects of global intelligence, fluid (Gf) and crystallized (Gc) intelligence, could be improved in adolescents with below-average IQ by using a game-based cognitive intervention. Method: Thirty-four adolescents participated in cognitive interventions targeting either Gf (GAMEf, n = 12) or Gc (GAMEc, n = 12) or were assigned to a control group (n = 10). Interventions took place two days a week for one hour, over 8 weeks. Standard neuropsychological assessments were conducted prior to and after the intervention to measure possible improvements in Gc (using the Wechsler Scales, WISC-IV), and Gf (using the Test Of Non verbal Intelligence, TONI-4). Results: Adolescents in the GAMEf program improved on measures of Gf, while adolescents in the GAMEc program improved on both measures of Gc and Gf. Conclusions: The results indicate that individuals with below average IQ can improve their fluid and crystallized intellectual functioning through direct cognitive training using commercially available games, suggesting that intellectual functioning at this level may be more susceptible to remediation than previously thought. These findings could have direct implications for cognitive intervention and learning potential in clinical populations with below average IQ.