Pesticides are an important and widely used tool for crop protection, but they also pose significant risks to agricultural sustainability, human health and the environment. In this paper, we examine whether mass media campaigns can help improve pesticide knowledge and change pesticide use behaviour among smallholder farmers in Rwanda and Uganda. We also assess the individual and combined effects of the campaign channels, which include interactive radio, plant health rallies, mobile SMS and video screenings. Applying a doubly robust method to survey data from 1327 maize-producing households across the two countries, we find that the mass media campaigns are significantly associated with improved farmer knowledge of pesticide risks and safety precautions. While the campaigns appear not to have discouraged the use of synthetic pesticides, they are significantly associated with increased adoption of safer alternatives to pesticides, including sustainable integrated pest management practices. The campaigns are also significantly correlated with increased use of protective equipment against pesticide exposure in both countries and reduced incidence of pesticide-related illnesses in Rwanda. We conclude that mass media campaigns (particularly using multiple complementary channels) can be effective in enhancing farmers’ knowledge about pesticide risks and safety measures, and promote the adoption of safer pest management strategies.