Introduction: In Mexico, marijuana consumption has increased in adults and university students, triggering problems in attention, concentration, anxiety, depression, dependence, and cardio-respiratory difficulties. Psychological interventions like brief motivational treatment (BMT) and cognitive behavioral therapy (CBT) have reported some difficulties such as a low and medium effect size, decreased consumption without reaching abstinence, and heterogeneity in the use of both cognitive and behavioral techniques. The use of behavioral techniques in Behavioral Activation has reported effectiveness in the treatment of anxiety, depression, and recently in alcohol and tobacco. Objective: to evaluate the effect size of a Behavioral Activation treatment in abstinence of marijuana (BA-M) measured in units, occasions, and quantity of consumption. Method: in a sample of university students (n = 8), the intervention of behavioral activation was applied, which includes functional analysis, planning and goal setting, contingency management, skills training, and relapse prevention. It was carried out a multielement single case design with eight replications, calculating the effect size through the non-overlapping index of all pairs. Results: high effect size was obtained in the consumption pattern, ranging between 91.10% and 100%, 5 university students achieved abstinence. Discussion and conclusions: treatment in BA-M obtained a high effect size in abstinence and a decrease in marijuana abuse these results are similar to those reported in alcohol and tobacco.