Uncertainty – here defined as lacking knowledge about what outcome will follow from what choices – is a pervasive challenge that we face when making decisions. While past research has focused on the role of uncertainty in individual decision-making, where our choices have outcomes only for ourselves, we know much less about how uncertainty shapes social decision-making, where our choices have outcomes not only for ourselves but also for others. Exploring uncertainty’s role in these decisions is important because the social domain is characterised by high levels of interdependence, complexity, and subjectivity – features that make it more difficult to predict how our decisions will affect others. Besides high levels of uncertainty, many social decisions involve trading off personal and social interests that come with high stakes, ranging from others’ physical or mental well-being to the subsistence of social institutions that rely on cooperation. This talk will discuss results from two lines of research which suggest that uncertainty in social decisions leads people to err on the side of caution. In particular, taking a comparative approach, we observe less risk seeking and pronounced indecision in social compared to individual decisions under uncertainty. We also show that uncertainty about the impact of our actions on others’ well-being reduces selfishness, at the benefit of prosociality.