Introduction Positive HIV results disclosure plays a significant role in the successful prevention and care of HIV infected patients. It provides significant social and health benefits to the individual and the community. Non-disclosure is one of the contextual factors driving the HIV epidemic in Uganda. Study objectives: to determine the frequency of HIV disclosure, associated factors and disclosure outcomes among HIV positive pregnant women at Mbarara Hospital, southwestern Uganda. Methods A cross-sectional study using quantitative and qualitative methods among a group of HIV positive pregnant women attending antenatal clinic was done and consecutive sampling conducted. Results The total participant recruitment was 103, of which 88 (85.4%) had disclosed their serostatus with 57% disclosure to their partners. About 80% had disclosed within less than 2 months of testing HIV positive. Reasons for disclosure included their partners having disclosed to them (27.3%), caring partners (27.3%) and encouragement by health workers (25.0%). Following disclosure, 74%) were comforted and 6.8% were verbally abused. Reasons for non-disclosure were fear of abandonment (33.3%), being beaten (33.3%) and loss of financial and emotional support (13.3%). The factors associated with disclosure were age 26-35 years (OR 3.9, 95% CI 1.03-15.16), primary education (OR 3.53, 95%CI 1.10-11.307) and urban dwelling (OR 4.22, 95% CI 1.27-14.01). Conclusion Participants disclosed mainly to their partners and were comforted and many of them were encouraged by the health workers. There is need to optimize disclosure merits to enable increased participation in treatment and support programs.