The objective of this research was to estimate the inhabitant’s Willingness-To-Pay (WTP) for improving Tlapaneco river water quality, located in the region of ‘‘Montaña de Guerrero’’, so that it returns to provide benefits that it provided before its polluted condition. To estimate WTP we applied Contingent Valuation Method (MVC). It allows revealing the amount of money people is willing to pay in order to maintain the well-being that produces the modification in the conditions of supply of an environmental good without price in the market. The population interviewed perceives that the water of the river is polluted and the benefits they used to obtain have reduced. It is the reason why they have changed his use. Results show that inhabitants are willing to contribute resources to improve the quality of the water flow. Variables age, schooling, number of members of the household and income are statistically significant at 95% confidence and they fit very well a Tobit linear model. In terms of public policy, results show feasibly to start up an intervention to reduce water pollution with the involvement of organized people from the communities of the studied region.