Skin cancer is one of the most common cancers in Iran. Farmers are exposed to the sun's ultraviolet radiation due to their job and are susceptible to skin cancer. The aim of this study is to survey the effect of educational intervention based on health belief model and social support on promoting skin cancer preventive behaviors in farmers of Fasa City, Fars province, Iran. In this quasi-experimental study, 200 farmers (100 in experimental group and 100 in control group) in Fasa City, Fars, Iran, were selected in 2017. The educational intervention for the experimental group consisted of eight training sessions (introduction to skin cancer, risk factors, complications, benefits and barriers to proper use of sunscreen, UV sunglasses and physical protection, self-efficacy in applying preventive behaviors, role of social support). A questionnaire consisting of demographic information, knowledge, HBM constructs (perceived susceptibility, severity, benefits, barriers, self-efficacy and cues to action), and social support was used to measure skin cancer preventive behaviors before, 3 months after the intervention, and 6 months later. Data were analyzed using SPSS-22 via chi-squared, independent samples t test, Mann-Whitney, and repeated measures ANOVA at a significance level of 0.5. The mean age of the farmers was 42.21 ± 10.52 years in the experimental group and 44.28 ± 10.16 years in the control group. Three months after the intervention and 6 months after the intervention, the experimental group showed a significant increase in the knowledge, perceived susceptibility, perceived severity, perceived benefits, self-efficacy, cues to action, social support, and skin cancer preventive behaviors compared to the control group. This study showed the effectiveness of the intervention based on the HBM constructs and social support in adoption of skin cancer preventive behaviors in 3 and 6 months post intervention in farmers. Hence, these models can act as a framework for designing and implementing educational interventions for the prevention of skin cancer.