Background: Internet-based intervention could help drug users recover from drug dependence. This study evaluated the effectiveness of a newly developed web-based relapse prevention program (e-SMARPP) for people with a drug problem, including the use of methamphetamine, in Japan. Methods: The study was a pilot randomized controlled trial comprised of 48 psychiatric outpatients diagnosed with drug use disorder. The participants were randomly assigned to an eight-week, six-session web-based relapse prevention program (an intervention group) or only web-based self-monitoring (a control group). The primary outcome was the duration of abstinence from a primary drug during the intervention and relapse risk. Secondary outcomes included motivation to change, self-efficacy, and money spent on drugs. The outcomes, except for the duration of abstinence during the intervention, were assessed at baseline, 2-, 5-, and 8-months. Program completion rate was also assessed. Results: No significant difference was observed between the intervention and the control groups for the primary and the secondary outcomes. The effect size of the duration of abstinence during the intervention was d = 0.42, which was comparable to previous studies. In the intervention group, about 26% did not complete the entire intervention. Conclusions: e-SMARPP failed to demonstrate efficacy, however, is potentially helpful for enhancing abstinence. The low attrition rate may suggest the acceptance and feasibility of the program. Further improvement of the program and evaluation in a full-scale trial are needed.