BACKGROUND: Mobile phone-based interventions have been demonstrated in different settings to overcome barriers to accessing critical psychosocial support. In this study, we aimed to assess the acceptability and feasibility of a phone-based, peer-to-peer support group intervention for adolescent pregnant women aged 15-24 years living with HIV in Zambia. METHODS: Sixty-one consenting participants were recruited from Antenatal Clinics of two large urban communities in Lusaka. They were invited to participate in the mobile phone-based intervention that allowed them to anonymously communicate in a small group led by a facilitator for 4 months. A mixed methods approach was used to assess acceptability and feasibility, including a focus group discussion, pre- and post-intervention interview and analysis of the content of the text message data generated. RESULTS: Participants reported finding the platform "not hard to use" and enjoyed the anonymity of the groups. Seventy-one percent of participants (n = 43) participated in the groups, meaning they sent text messages to their groups. Approximately 12,000 text messages were sent by participants (an average of 169 messages/user and 6 mentors in 6 groups. Topics discussed were related to social support and relationships, stigma, HIV knowledge and medication adherence. CONCLUSION: The study showed that the intervention was acceptable and feasible, and highlighted the potential of the model for overcoming existing barriers to provision of psychosocial support to this population.