In Ethiopia, there have been increased efforts to promote market-oriented vegetable production. Given that food security is a crucial issue in Ethiopia, the question is whether market-oriented vegetable production will actually help farmers to become more food secure. Using a mixed methods approach, the present research gathered empirical evidence on the determinants of participation in the vegetable business and its food security impacts in the Raya Azebo district. The Heckman two-stage selection model was used to identify factors affecting participation in the vegetable business and its effects on several food security outcomes. A thematic analysis was applied to the qualitative data. The results show that a farmer’s participation in the vegetable business increased significantly with adequate household productive resources (e.g., land size and access to irrigation), cooperative memberships and access to extension services. On the other hand, the age of the head of household, the market distance and risk perceptions significantly decreased participation. Additionally, the results indicate participation in the vegetable business results not only in higher food availability and access but also in lower food variety and diet diversity scores. Participation has less of an impact on per capita kilocalorie consumption and child anthropometric measures of food security. The policy implication is that, while Ethiopia is going ahead with inclusive market-driven approaches to food security, alternative mechanisms must be put in place to address the negative impacts and to empower those living in the most vulnerable conditions.