Objective: While many studies suggest that regular cannabis use leads to deficits in cognitive functioning, particularly in memory (Schreiner & Dunn, 2012), few have measured effort put forth during testing, let alone examined this as a potential mediator. The present study investigated the relationship between frequency of cannabis use and effort among cannabis users, and sought to determine whether effort mediated the relationship between cannabis use and learning and memory performance. Method: Sixty-two participants who met criteria for chronic cannabis use (four or more days per week for at least 12 months) completed a neuropsychological battery including the California Verbal Learning Test, second edition (CVLT-II) as a measure of memory, and the Word Memory Test (WMT) as a measure of effort. Results: Analyses revealed a significant relationship between frequency of use and WMT performance (p < .01, 95% CI), suggesting that participants who more frequently used cannabis exhibited poorer effort. Bootstrapping yielded confidence intervals for indirect effects (Shrout & Bolger, 2002), and revealed that effort (i.e., WMT performance) significantly mediated the relationship between frequency of cannabis use and CVLT-II Learning (sum of Trials 1-5; p < .01, 95% CI), as well as CVLT-II Delayed Recall (p < .01, 95% CI). Interestingly, frequency of use also demonstrated a direct, positive relationship with CVLT-II Learning (p < .02, 95% CI). Conclusion: Findings indicate that effort mediates the relationship between frequency of cannabis use and performance on verbal learning and memory, suggesting that effort should be measured and controlled for in future studies. Implications will be discussed.