The feeling of inequality as a factor disrupting social order is a significant preventing element for cooperation. To evaluate the impact of feelings of inequality mechanism on cooperation, the “rational choice theory” was selected due to the impact of feelings of inequality on actors’ rational choice and its capacity to explain the problem from various aspects.It was assumed that the feeling of inequality affect four types of rationalities, including instrumental, practical-authoritative, collective-particularistic, and formal- universal rationalities, has some effects on cooperation. Its effect also proceeds via variables consisting rationality, that is, egoistic individualism, myopic rationality, social anxiety, social trust, societal identity, and non-consequential ethic.The present study has been carried out by survey method among 343 people aging over 18, living in Tehran that selected through cluster- random sampling in micro level. Stepwise regression technique shows that the feeling of inequality decreases cooperation via decreasing the formal-universal and collective-particularistic rationality, and increasing the instrumental rationality. The feeling of inequality decreases cooperation mostly via the variables of social identity, non-consequential ethics, and egoistic individualism.