Recent studies suggest that recreational use of cocaine is associated with significant impairments in the same cognitive control functions that are affected by chronic use. Here we tested whether recreational cocaine use can impact the emergence and resolution of response conflict in conflict-inducing tasks. Recreational cocaine polydrug users (n = 17) and cocaine-free controls (n = 17), matched for sex, age, intelligence, and alcohol consumption, performed a Simon task-which is known to induce response conflict. Recreational users showed a larger Simon effect, indicating that they had more difficulty resolving stimulus-induced response conflict. This finding is consistent with the recent literature showing that even small doses of cocaine are sufficient to compromise key cognitive control functions.