BACKGROUND: Adherence to TB treatment and therefore treatment success could be improved using digital adherence technology. OBJECTIVE: To evaluate the effectiveness of a medication event reminder monitor system (MERM) on treatment success and treatment adherence in patients with drug-susceptible pulmonary TB in Perú. METHODS: This was an experimental, randomised, open-label, controlled study conducted among patients in the second phase of TB treatment. The intervention group received their medications through MERM with the support of a treatment monitor, whereas the control group used the usual strategy. Participants were followed until they completed the 54 doses of the second phase of treatment. RESULTS: The study included 53 patients in each group; four in the intervention group withdrew from the study. Treatment success was significantly more frequent in the MERM group (RR 1.15, 95% CI 1.02–1.30; P = 0.0322). There was no significant difference in the adherence outcomes; however, the percentage of patients who missed at least one dose and patients with more than 10% of total doses missed were lower in the intervention group. CONCLUSION: The use of MERM in the second phase of treatment showed a significant improvement in the treatment success rate in patients with drug-susceptible pulmonary TB.