In the past half century, increasing agricultural lands by deep well pumping have led to many problems such as groundwater depletion, drying of Qanats, land subsidence, environmental problems and declining water quality. Despite the dominance of administrative water management mechanism, there is evidence of successful community-based groundwater governance. The aim of this study is to exploring collective action of farmers in groundwater pumping control using Ostrom's social-ecological system framework in Ghomshe and North Mahyar areas in Shahreza county. A combination of quantitative and qualitative approaches was employed. Data were collected using observation, open and structured interview and documentary research. The Results showed that community-based water management and natural features of Ghomshe area are the main cause of water resources sustainability. The existence of social capital, long history of water management, farmers' livelihood dependence on water access, farmers residing, small land area, being away from the city and the provincial capital and no governmental investment in irrigation infrastructure has provided relative stability of traditional self-governance. On the other hand, although still seen farmer’s collective action of groundwater management in Mahyar village, shared aquifer between this village and Mahyar plain bring about overuse of the aquifer. The overall result of this study indicated that contrary to the expectations of policy makers, informal collective action of farmers is an effective governance in groundwater pumping control and protection. Key words: Collective action, Groundwater, Common pool resource, Social-ecological system framework, North Mahyar, Ghomshe.