The internet of things has revolutionized Chinese agricultural production and marketing sectors, creating “New Farmers.” WeChat is one of the most popular social media platforms in China, and WeChat marketing of agricultural products has become a widespread phenomenon. To respond to the quality and safety concerns of consumers on the social media marketing platform, New Farmers should pay more attention and maintain the quality and safety of the agricultural products they sell on WeChat. Our objective is to understand the determinants influencing the New Farmers' quality and safety knowledge of the fresh fruits they sell on WeChat. For this purpose, we collected data in 2018 from a sample of 504 purely sales-oriented New Farmers in China. We analyzed the influence of WeChat marketing, food safety awareness, personal characteristics, and external factors on purely sales-oriented New Farmers' quality and safety knowledge related to the fresh fruits they sell on WeChat based on the Stimulus-Organism-Response framework. Results indicated that purely sales oriented New Farmers' ranking of their understanding of the quality and safety status (pesticides, fertilizers, and quality and safety certifications) of the fruits depend on factors such as consumers' consultation frequency about quality and safety information to New Farmers, consumers' word of mouth, sales status of fruits, WeChat regulation, quality and safety awareness of New Farmers, gender, training received, government regulations, and consumers attention to food safety. The findings should be helpful to strengthen the quality and safety management, training, and supervision of New Farmers.