The objective of this study was to determine if introducing acceptance and commitment therapy in the prevention of mother to child HIV transmission (PMTCT) programme using weekly mobile phone messages would result in improved mental health status of HIV-positive, pregnant women in Nigeria. We used a Solomon four-group (two intervention and two control groups) randomised design. The study population was 144 randomly selected, HIV-positive pregnant women attending four randomly selected PMTCT centres in Nigeria. The intervention groups were exposed to one session of acceptance and commitment therapy with weekly value-based health messages sent by mobile phone for three months during pregnancy. The control groups received only post-HIV test counselling. A total of 132 participants (33 per site) were enrolled in the study from the two intervention and two control sites. In the pre-tests, the intervention and control groups did not differ significantly with regard to demographics. Evaluation of the pre- and post-tests of the intervention group indicated significantly higher Action and
Acceptance Questionnaire (AAQ-II) scores. The introduction of a mobile phone acceptance and commitment therapy programme may result in greater psychological flexibility in women diagnosed with HIV.