exico is the largest soft drink market in the world, with high rates of obesity and type 2 diabetes. Due to strains on the nation’s productivity and healthcare spending, Mexican lawmakers implemented one of the world’s first public health taxes on sugar-sweetened beverages (SSBs) in 2014. Because Mexico’s tax was designed to reduce SSB consumption, it faced strong opposition from transnational food and beverage corporations. We analysed previously secret internal industry documents from major corporations in the University of California San Francisco’s Food Industry Documents Archive that shed light on the industry response to the Mexican soda tax. We also reviewed all available studies of the Mexican soda tax’s effectiveness, contrasting the results of industry-funded and non-industry-funded studies. We found that food and beverage industry trade organisations and front groups paid scientists to produce research suggesting that the tax failed to achieve health benefits while harming the economy. These results were disseminated before non-industry-funded studies could be finalized in peer review. Mexico still provided a real-world context for the first independent peer-reviewed studies documenting the effectiveness of soda taxation—studies that were ultimately promoted by the global health community. We conclude that the case of the Mexican soda tax shows that industry resistance can persist well after new policies have become law as vested interests seek to roll back legislation, and to stall or prevent policy diffusion. It also underscores the decisive role that conflict-of-interest-free, peer-reviewed research can play in implementing health policy innovations.