Women play critical roles in agricultural value chains in developing countries. However, their participation in value chain development activities does not always result into their empowerment. The main objective of this study was to examine the impacts of women participation in onion value chain development activities on their empowerment. The study was conducted in Simanjiro District and adopted a cross-sectional research design. Qualitative and quantitative data were collected using focus group discussions, key informant interviews and household surveys whereby 402 women of whom 207 (51.2%) were participants in the onion value chain development activities and 195 (48.5%) were non-participants. Moreover, eight focus group discussions were conducted. Qualitative data were analyzed using ethnographic content analysis technique with constant comparison; quantitative data were analyzed using the Statistical Package for Social Sciences. Descriptive statistics were computed to establish the profiles of research participants; gross margin were calculated to establish profit margins of different chain actors; Cumulative Empowerment Index was constructed to gauge the overall women empowerment. Principle Component Analysis was used to compute wealth quintiles as proxy for household socio-economic status. F-test was used to compare the levels of empowerment by socio-economic status. Ordinal logistic regression model was used to establish the determinants of women empowerment in onion value chain. Changes in gender roles, especially in production, were found. Women‟s perception on their empowerment was linked to different achievements in their lives in their social and economic contexts and was categorized into medium level of empowerment (CEI = 0.6033). Women participation in decision making was higher and farmer groups were an important source of knowledge for change. The relationship between socio-economic status and women empowerment was statistically significant (P < 0.05). Ordinal logistic regression analysis revealed the predictors of women empowerment in the chain to be: marital status, education level, age at first marriage, land ownership, access to credit and participation in onion value chain (P < 0.05). It is recommended to the government and non-governmental organisations to promote men‟s involvement in women empowerment efforts, to improve women access to resources and strengthen farmer‟s organisations to competitively participate and get benefits from onion value chain.Government of Tanzania through its Commission for Science and Technology (COSTECH)