Enhancing the efficiency of vegetable farms is crucial to increase the vegetable outputs for meeting the demand for growing population. This study evaluated the technical efficiency and explored factors determining the efficiencies of smallholder vegetable farms in diversified agro-ecological regions using Stochastic Frontier Analysis (SFA) with cross-section data collected in 2013. The results revealed that average technical efficiency was found to be 0.77 and the variance parameters were highly significant indicating that the inefficiency existed in vegetable farms. The inefficiency gap could improve by operating the farms at the frontier level. The input variables consisting of land, labor, animal power, fertilizer, compost, pesticide, and capital were proved to be the important factors in determining the level of outputs. Meanwhile, the major sources of the inefficiencies identified were: age of farmer, training to the farmers, and infrastructure development. The efficiency in vegetable production can be improved by allocating input resources at the optimum levels, encouraging younger farmers in vegetable production, increasing training and extension activities, enhancing market access to the farmers, and developing infrastructures with regard to vegetable production.