Background: In developing world including Ethiopia, agricultural productivity was very low; especially where production is common on fragile lands and characterized by smallholder subsistence farming. One of the main reasons for low productivity is the inability of farmers to fully exploit available technologies and production techniques. Considering this in to account, this study analyzes the technical efficiency and its possible source of inefficiency in smallholder tomato farming in Siltie Zone Southern Ethiopia. Methods: By using three stage sampling, 175 randomly selected smallholder tomato farmers were sampled and stochastic frontier Cobb Douglas production model was applied. Results and Conclusion: The results indicate that the mean technical efficiency among smallholder tomato farmers is 81.7%, implying a potential to increase tomato production by 19.3% with the current level of resources and technology. The study further revealed that output responds positively to increases in technological factors of production. According to estimates of the inefficiency model among various factors sex of household head, frequency of weeding, diseases incidence and type of variety used were found to significantly affect the level of technical efficiency of tomato crop producers. Thus, development policies in the tomato sub sector might focus more on empowering women in resource allocation, adoption of high-yielding and disease-resistant tomato varieties and better management of tomato plantations might reduce technical inefficiency among tomato farmers in the study area.