Uncertainty is an integral part of science, statistics, and measurement. Yet in a post-truth world in which (political) ideologies can trump quantitative evidence and scientific reasoning, there can be anxiety among scientists, experts, and policy-makers that highlighting uncertainty about scientific facts and numbers will only serve to further decrease trust and credibility. Interestingly, there has been little research so far that examined the effects of communicating uncertainty about facts and numbers. We are conducting a set of experimental studies to test under what conditions communicating uncertainty about numbers and facts does – and does not – influence comprehension and trust. The first experiment (N = 1126, online experimental survey study) examined how people react to uncertainty (vs. no uncertainty) when communicated as a numerical range versus a verbal statement about three different facts (number of tigers in India vs. UK unemployment rate vs. increase in global surface temperature over the past century). As might be expected, the results showed that across all these topics, people perceived estimates about which uncertainty was communicated as more uncertain than when no uncertainty was communicated; and this effect was stronger for verbal uncertainty communication. In addition, people perceived estimates about which uncertainty was communicated as less reliable and trustworthy, but mostly so for verbal uncertainty communication; the effects for numerical uncertainty communication were small. Interestingly, for numerical uncertainty communication, there was no difference (compared to no uncertainty communication) in how trustworthy the source of the numbers was perceived. This indicates that people distinguish between the numbers themselves and the source in their judgments: Whereas the numbers were seen as less trustworthy, in the case of numerical uncertainty communication the trustworthiness of the source was unaffected. In the second experiment (currently in progress), we will investigate the impact of the magnitude of the uncertainty on these effects and examine various kinds of numbers (relative vs. absolute). Our results provide a first indication that communicating uncertainty does affect people’s interpretation of numbers and of the organization or source behind it. The generalizability of these results, avenues for future research, and implications for communicators of numbers will be discussed.