Background: Chronic consumption of alcohol and marijuana, especially when initiated at an early age, has been implicated in cognitive alterations in the domain of executive functioning. Despite the robustness of this finding in Western populations, its generalizability to other cultural contexts is largely unknown. In this study, we examined whether the regular use of alcohol or marijuana use relates to impaired executive functioning in male students of a Nigerian university. Methods: Chronic alcohol users (n = 39), chronic marijuana users (n = 35) and drug-abstinent control participants (n = 40) recruited through snow-ball sampling technique completed a computerized version of the Wisconsin Card Sorting Test (cWCST). As an established measure of executive functioning, the cWCST allows for the simultaneous assessment of three distinct executive processes: set shifting, rule inference, and set maintenance. Results revealed a selective set-shifting deficit in both alcohol and marijuana users. Results: Both groups committed significantly more perseverative errors than the control group, and group differences were significantly stronger on this indicator of set shifting than on indicators of rule inference or set maintenance. Conclusions: Our findings support the generalizability of drug-related deficits in executive functioning and contribute to the characterization of executive dysfunction in non-Western populations. Future longitudinal studies are required to clarify whether executive dysfunction is an antecedent or consequence of alcohol and marijuana use in young Nigerians.