OBJECTIVE Given the widespread use of cannabis, and the concomitant risks associated with the drug, there is a need to increase the availability of interventions designed to reduce risky cannabis use. One promising intervention in the addictions employs personalized normative feedback to motivate change. METHODS A two-arm randomized controlled trial (RCT) was conducted in which participants who used cannabis in a risky fashion were randomly assigned to one of two groups - those who received an online personalized feedback report in addition to educational materials about risky cannabis use and those who just received the online educational materials. Follow-up assessment occurred at three- and six-months post-randomization. Outcome variables included: number of days cannabis was used in the past 30, risky cannabis use (ASSIST score of four or more), and participant estimates of the proportion of cannabis users among those of the same age and gender. RESULTS A total of 744 participants with risky cannabis use were recruited for the trial using online advertisements. There were no significant differences between intervention and educational materials only groups at three- and six-month follow-ups for the outcome variables, number of days used cannabis in the last 30 (p = 0.927) and proportion of participants engaging in risky cannabis use (p = 0.557). At three and six month follow-ups, participants who received the feedback intervention were more likely than those in the educational materials group to estimate that a larger proportion of people their age and gender did not use cannabis in the last year (p = 0.028). CONCLUSIONS While there was some evidence that the personalized feedback intervention modified normative perceptions about cannabis use, there did not appear to be support for the prediction that the intervention reduced cannabis consumption.