Increased attention has recently been given to technical efficiency of small-scale irrigation to achieve food security and increase agricultural development. In this paper, the authors classify irrigation supply management methods as cooperative or non-cooperative, introduce social capital by four dimensions (social network, social trust, social reputation, and social participation), and highlight the impacts of both social capital and cooperative agreements on technical efficiency in the context of small-scale irrigation management. Efficiency is assessed using data envelopment analysis (DEA), and the impact of cooperative agreements and social capital on efficiency is estimated using path analysis. The result of DEA indicates that cooperative and social capital can improve technical efficiency of irrigation. Results of path analysis show that the presence of a cooperative has a positive, significant and direct impact on efficiency. Additionally, the effect of social capital on efficiency is estimated to be reinforced via participation in cooperative methods.