Breastfeeding has been shown to benefit both maternal and child immune status. The impact of exclusive breastfeeding in the presence of HIV infection on maternal and child health is still unclear. Socio-economic factors make breast-feeding an important source of nutrition for an infant 6 months and under in the developing world. A prospective study was conducted to examine the impact of feeding mode on various maternal indices including anthropometry; body composition indicators (using FTIR); haematology and biochemical markers; as well as incidence rates of opportunistic infections and clinical disease progression. In infants we examined the impact on growth, development and morbidity. AFASS criteria (affordable, feasible, accessible, sustainable and safe) were fulfilled by 38.7% of the formula feeding mothers. No significant differences between the formula feeding and breastfeeding groups in terms of haematological, immunological and body composition changes were seen. Breastfeeding mothers had significantly lower events with high depression scores (P = 0.043). Breastfeeding infants had a significantly lower risk of diarrhoea and hospitalisation at 3 months (P = 0.006 and 0.014 respectively). Breastfeeding was significantly associated with better development scores and growth parameters. Breastfeeding is not harmful to the mother in the presence of HIV infection. Mothers are still choosing formula feeding inappropriately despite counselling about the AFASS criteria. Breastfeeding is beneficial to the infants especially in the first 3 months of life.