The objective of this study was to assess the acceptability and feasibility of a cell phone based case manager intervention targeting HIV-infected pregnant women on highly-active antiretroviral therapy (HAART). Pregnant women ≥36 weeks gestation attending antenatal care and receiving HAART through the Option B+ program at a primary care clinic in South Africa were enrolled into a prospective pilot intervention to receive text messages and telephone calls from a case manager through 6 weeks postpartum. Acceptability and feasibility of the intervention were assessed along with infant HIV testing rates and 10-week and 12-month postpartum maternal retention in care. Retention outcomes were compared to women of similar eligibility receiving care prior to the intervention. Fifty women were enrolled into the pilot from May to July 2013. Most (70%) were HAART-naive at time of conception and started HAART during antenatal care. During the intervention, the case manager sent 482 text messages and completed 202 telephone calls, for a median of 10 text messages and 4 calls/woman. Ninety-six percent completed the postpartum interview and 47/48 (98%) endorsed the utility of the intervention. Engagement in 10-week postpartum maternal HIV care was >90% in the pre-intervention (n = 50) and intervention (n = 50) periods; by 12-months retention fell to 72% and was the same across periods. More infants received HIV-testing by 10-weeks in the intervention period as compared to pre-intervention (90.0 vs. 63.3%, p