This paper evaluates the determinants of onion profitability among smallholder farmers at Mlembule Ward. Specifically, the paper determines onion profitability status, examines determinants of onion profitability and assesses strategies for improving profitability. The paper employed a cross-sectional research design whereby structured and semi-structured interviews, focus group discussions and documentary review methods werere used for data collection. Probability and non-probability sampling techniques were employed to select a sample of respondents and key informants respectively. Data analysis employed in this study included both inferential and descriptive statistics. The findings depicted that, average gross profit, average net profit and profit margins were higher in the dry season compared to the rainy season. Binary logistic regression analysis indicated that, sex (0.047), education (0.029), capital (0.049), seeds variety (0.011), market access (0.05), market prices (0.034), credits access (0.034), irrigation technology (0.05), fertilizer (0.032) and farm size (0.016) significantly affected the profitability of onion at p<0.05. The main strategies employed for profitability were wholesale selling, improving yield quantity and quality and formingWater Users Association (WUA). Therefore, community efforts, credit availability, research and financial support from the Ministry of Water and Irrigation and interested development partners have to improve profitability. Empowering marketing associations, improving market and irrigation infrastructures and extension services provision through the ditrict council have to improve onion profitability.