We examined how different types of communication influence people's responses to health advice. We tested whether presenting COVID-19 prevention advice (e.g., washing hands/distancing) as either originating from a government or scientific source would affect people's trust in and intentions to comply with the advice. We also manipulated uncertainty in communicating the advice effectiveness. To achieve this, we conducted an experiment using large samples of participants (N = 4,561) from the United Kingdom, the United States, Canada, Malaysia, and Taiwan. Across countries, participants found messages more trustworthy when the purported source was science rather than the government. This effect was moderated by political orientation in all countries except for Canada, while religiosity moderated the source effect in the United States. Although source did not directly affect intentions to act upon the advice, we found an indirect effect via trust, such that a more trusted source (i.e., science) was predictive of higher intentions to comply. However, the uncertainty manipulation was not effective. Together, our findings suggest that despite prominence of science skepticism in public discourse, people trust scientists more than governments when it comes to practical health advice. It is therefore beneficial to communicate health messages by stressing their scientific bases. (PsycInfo Database Record (c) 2023 APA, all rights reserved).