In this study, we assessed the feasibility and effectiveness of the Adolescent Cannabis Check-Up (ACCU), a brief intervention for young cannabis users. For this initial feasibility study, we used an uncontrolled pre-test/post-test design. Participants were cannabis users aged between 14 and 19 years (n = 73) and concerned parents (n = 69). The intervention comprised an individual assessment session followed 1 week later by a session of personalized feedback delivered in a motivational interviewing style. An optional third session that focused on skills and strategies for making behavioral change was offered. Of the entire sample of cannabis users, 78% reported voluntarily reducing or stopping their cannabis use during the 90 days to follow-up and 16.7% reported total abstinence during this time. In addition, significant reductions were found on measures of both quantity and frequency of use and dependence. These reductions were maintained at 6-month follow-up. Clearly, these preliminary findings must be interpreted with caution given the study design and absence of a control group. The ACCU was, however, able to attract and retain young cannabis users who were not necessarily interested in change. The approach was acceptable to young people and associated with reductions in cannabis use. It appears to be a model that warrants further research in early and brief interventions for this population.