• Offenders demonstrated average IQ, with better performance IQ than verbal IQ.
• The evenness of the cognitive profile needs to be considered in offenders.
• Aggressive behaviors were related to problems with response inhibition.
• Executive deficits may be important in relation to age at onset of criminality.
Studies have shown that offenders have impaired cognitive abilities yet it is unclear if cognitive dysfunction per se contributes to aggressive antisocial behaviors. Our aims were to (1) determine associations between cognitive functioning and different forms of aggressive antisocial behaviors, (2) describe prevalence of, and covariates to, uneven intellectual profiles, and (3) investigate associations between cognitive functioning and age at onset of aggressive antisocial behaviors. A cohort (n = 269) of 18–25 years old male violent offenders were assessed for general intellectual functioning with the Wechsler Adult Intelligence Scales–third edition, and for executive functions with the Cambridge Neuropsychological Test Automated Battery. Only one measure of cognitive functioning – slower reaction times in a response inhibition test – was significantly correlated with higher occurrence of aggressive, but not exclusively antisocial, behaviors. Furthermore, offenders with even intellectual profiles showed more aggressive antisocial behaviors than offenders with uneven intellectual profiles. Finally, increased errors in tests of cognitive flexibility and slower reaction times in a response inhibition test were associated with a younger age at onset of general, but not exclusively violent, criminality. Overall, effect sizes were small. The findings emphasize the need of research investigating how cognitive functioning in offenders affects susceptibility to treatment interventions.