Abstract: During the critical agricultural green transformation period, dividing social support into two dimensions (material and emotional) and exploring the impact of social support on the cultivated land quality protection behavior of farmers is of great significance for promoting coordinated development of the rural revitalization strategy and construction of an agricultural ecological civilization. Based on survey data from 945 farmers in Hubei Province, this study empirically examined the influence and mechanism of social support on the cultivated land quality protection behavior of farmers using the probit, mediating effect, and moderating effect models. The research results showed that: 1) Both material and emotional support could significantly promote the cultivated land quality protection behavior of farmers, and compared with material support, emotional support had greater significant impacts on this behavior. 2) The impact of material and emotional support on the cultivated land quality protection behavior of farmers varied among farmers with different capital endowments. Compared to elderly farmers and low-income farmers, material and emotional support had a more distinct promotion effect on the behavior of young farmers and high-income farmers in protecting the quality of cultivated land. 3) Both material and emotional support promoted farmers’ participation in the protection of cultivated land quality by improving information capability, and the proportions of the mediating effect in the total effect were 0.039 and 0.028, respectively. 4) Command-and-control environmental regulations significantly enhanced the promoting effect of material and emotional support on farmers’ participation in the protection of cultivated land quality, whereas the effect of incentive-based environmental regulations was not significant. Therefore, cultivating a dual-pronged material and emotional support model, establishing an information system service platform, improving the environmental regulation system, and reasonably implementing differentiated policies based on farmers’ capital endowments are important measures to promote the precise protection of cultivated land quality and realize the goal of agricultural green transformation.