Background Despite low pregnancy intentions, many women accessing contraception discontinue use, increasing the risk of unwanted pregnancies among women living with HIV (WLWH). We evaluate whether a family planning support intervention, inclusive of structured immediate one-on-one postpartum counseling, and a follow-up mechanism through additional health information and SMS reminders affects continuous contraceptive use and pregnancy incidence among recently postpartum WLWH. Methods We performed a randomized controlled trial between October 2016 and June 2018 at a referral hospital in southwestern Uganda. We included adult WLWH randomized and enrolled in a 1:1 ratio to receive family planning support or standard of care (control) and completed an interviewer-administered questionnaire at enrolment, 6 and 12 months postpartum. Our two primary outcomes of interest were; continuous use of contraception, and incidence of pregnancy. Secondary outcomes included contraception uptake, method change, discontinuation and pregnancy intentions. The trial was registered with clinicaltrials.gov (NCT02964169). Results A total of 317(99%) completed all study procedures. Mean age was 29.6 (SD = 6.0) vs 30.0 (SD = 5.9) years for the intervention vs control groups respectively. All women were enrolled on ART. Total women using contraception continuously were 126 (79.8%) in the intervention compared to 110 (69.2%) in control group (odds ratio (OR) = 1.75; confidence interval (CI) = 1.24-2.75, P = 0.003). Pregnancy rates were 2% (N = 3) in the intervention vs 9% (N = 14) in the control group (OR = 0.20, 95% CI = 0.05-0.62, P = 0.006). Pregnancy intention was lower in the intervention vs control group (OR = 0.23, 95% CI = 0.08-0.64, P = 0.002). Women actively enrolled on contraception reduced more in the control compared to the intervention group (OR = 3.92, 95% CI = 1.66-9.77, P = 0.001). Women enrolled on each contraceptive method did not differ by group except for implants. More women initiating contraception use within three months postpartum had better continued use for either intervention (N = 123, 97.6% vs N = 3,2.4%) or control group (N = 86,78.2% vs N = 24,21.8%). Method-related side effects were less reported in the intervention group (OR = 0.25, 95% CI = 0.10-0.60, P = 0.001). Conclusion We found that sustained and structured family planning support facilitates continuous use of contraception and lowers rates of pregnancy amongst postpartum WLWH in rural southwestern Uganda. Women who initiated contraception within three months postpartum were more likely to maintain continuous use of contraception than those initiating later. Further evaluation of actual and perceived facilitators to the continuous contraception use by this support intervention will help replication in similar settings.