We implemented a group randomized controlled trial in 24 reproductive and child health clinics in eight districts in Mbeya region. Three months pre-intervention, we identified 1924 and 1226 patients established on antiretroviral therapy for six months or more in intervention and control clinics, respectively, of whom 83.4% and 86.9% had one or more post-intervention visits. The unadjusted rate of missed visits declined from 36.5% to 34.4% in intervention clinics and increased from 38.9% to 45.5% in control clinics following the intervention. Interrupted time series analyses demonstrated a net decrease of 13.7% (95% CI [-15.4,-12.1]) for missed visits at six months post-intervention. Similar differential changes were observed for visits missed by 3, 7, 15, or 60 days. Appointment-tracking and community outreach significantly improved appointment-keeping for women on antiretroviral therapy. The facility staff controlled their workload better, identified missing patients rapidly, and worked with existing community organizations. There is now enough evidence to scale up this approach to all antiretroviral therapy and Option B+ reproductive and child health clinics in Tanzania as well as to evaluate the intervention in medical clinics that treat other chronic health conditions.