Introduction Retention in HIV care and adherence to antiretroviral therapy (ART) during pregnancy and postpartum for women living with HIV (WLWH) are necessary to optimize health outcomes for women and infants. The objective of this study was to evaluate the impact of two evidenced‐based behavioural interventions on postpartum adherence and retention in WLWH in Kenya.MethodsThe Mother‐Infant Visit Adherence and Treatment Engagement (MOTIVATE) study was a cluster‐randomized trial enrolling pregnant WLWH from December 2015 to August 2017. Twenty‐four health facilities in southwestern Kenya were randomized to: (1) standard care (control), (2) text‐messaging, (3) community‐based mentor mothers (cMM) or (4) text‐messaging and cMM. Primary outcomes included retention in care and ART adherence at 12 months postpartum. Analyses utilized generalized estimating equations and competing risks regression. Per‐protocol analyses examined differences in postpartum retention for women with high versus low levels of exposure to the interventions.Results We enrolled 1331 pregnant WLWH (mean age 28 years). At 12 months postpartum, 1140 (85.6%) women were retained in care, 96 women (7.2%) were lost‐to‐follow‐up (LTFU) and 95 (7.1%) were discontinued from the study. In intention‐to‐treat analyses, the relative risk of being retained at 12‐months postpartum was not significantly higher in the intervention arms versus the control arm. In time‐to‐event analysis, the cMM and text arm had significantly lower rates of LTFU (hazard ratio 0.44, p = 0.019). In per‐protocol analysis, the relative risk of 12‐month postpartum retention was 24–29% higher for women receiving at least 80% of the expected intervention compared to the control arm; text message only risk ratio (RR) 1.24 (95% confidence interval [CI] 1.16–1.32, p<0.001), cMM only RR 1.29 (95% CI 1.21–1.37, p<0.001) and cMM plus text RR 1.29 (1.21–1.37, p<0.001). Women LTFU were younger (p<0.001), less likely to be married (p<0.001) and more likely to be newly diagnosed with HIV during pregnancy (p<0.001). Self‐reported ART adherence did not vary by study arm.ConclusionsBehavioural interventions using peer support and text messages did not appear to improve 12‐month postpartum retention and adherence in intention‐to‐treat analyses. Higher levels of exposure to the interventions may be necessary to achieve the desired effects.