At present, environmental crises caused by irresponsible agricultural activities are known to increase environmental vulnerability around the world. So, it is important to know how people think about the environment, what they know, and how concerned they are with nature and the environment. This survey research was aimed at understanding the pro-environmental behavior and its influencing factors among the apple orchardists of the Dena Kooh area of Semirom County. The population consists of 4019 horticultural producers in 28 villages in the Dena Kooh district, and the sample size was determined by random cluster sampling regarding the economic status of villages in two rich and poor clusters. 320 interviews were carried out with all sample members. The data collection instrument was a structured questionnaire, and its face validity was confirmed by Yasouj University faculty members. The Cronbach's alpha coefficient was calculated between 0.61 and 0.92, indicating acceptable reliability of the measures. The results showed that the average environmental behavior of the orchardists is at a poor level. A comparison of the average current and past environmental behavior of orchardists showed that their pro-environmental behavior has developed. The results of hierarchical regression showed that knowledge, responsibility, socio-cultural norms, values and emotions, external commitment, and past behavior accounted for 69% of the variance in orchardists’ environmental behavior in the economically rich cluster. The results of hierarchical regression in the economically poor cluster showed that emotions, knowledge, responsibility, socio-cultural norms, external commitment, and past behavior accounted for 75% of the variance in orchardists' environmental behavior. The current research can benefit policymakers, researchers, and farmers in determining pro-environmental practices, considering the viewpoints of farmers. However, various issues identified in this study have implications for future research and for other crops under different farming systems.