Human activities are the most effective and significant cause of environmental changes, some of which are destructive and others are beneficial. One of the most effective steps to protect the environment is to assess farmers’ behavior in achieving the goals of environmental sustainability. This study aimed to analyze the environmental sustainability behavior of farmers using the norm activation theory (NAT) in a questionnaire-based survey. The statistical population comprised wheat farmers in Kermanshah province, Iran ( N = 126,900). The sample size was determined to be 382 farmers by Krejcie and Morgan’s table. The validity of the questionnaire was verified by experts and its reliability was confirmed by a pilot test and calculating Cronbach’s alpha. Five variables of perceived behavior control, perceived self-efficacy, ascription of responsibility, denial of responsibility, and awareness of consequences had significant effects on personal norms. The variable of personal norms had a significant effect on farmers’ sustainable behavior. By and large, it can be concluded that NAT can adequately account for the environmental sustainability of farmers.