In normal circumstances breastfeeding is the best method for infant feeding but it is not considered safe in this HIV era because breast milk has the HIV virus. Exclusive Replacement Feeding is the best option for feeding the baby among HIV positive mothers and is recommended when it is accessible, feasible, affordable safe and sustainable (AFASS). WHO recommend stopping breastfeeding when Exclusive replacement feeding is AFASS. To prepare replacement foods and feed the baby for several times per day for many months is challenging. HIV positive mothers who have opted for exclusive replacement feeding face many challenges so they need help to succeed. Objective: The objectives of the study were to explore challenges faced by HIV positive mothers who opted for exclusive replacement feeding in Moshi Municipality. Study design: Exploratory cross sectional study design which used qualitative research approaches. Setting: This study was conducted in three care and treatment centers (CTC) of Moshi Municipality in Kilimanjaro region namely, Kilimanjaro Christian Medical Centre, Mawenzi hospital and Pasua health centre. Methodology: In depth interviews and focus group discussion were used to collect data from HIV positive mothers who were attending paediatric CTC. Results: A total of 39 participants participated in this study. The main themes emerged were:- social cultural challenges, psychological challenges, economic challenges, social support and coping mechanism. The age of participants was between 20 and 42 years, majority were married 19% and those had primary education were 21%. Data was analyzed manually using thematic analysis where by themes and sub-themes were extracted and analyzed. Conclusion: HIV positive mothers who are practicing exclusive replacement feeding face many challenges. These challenges need to be addressed by plan interventions which will address them to make the life of such mothers better and to improve this method of infant feeding. Recommendation: The study recommends strengthening male involvement in the counselling for infant feeding options in order to maximize social support needed to promote ERF and minimize stima.