Politicians learning about public opinion and responding to their resulting perceptions is one key way via which responsive policy-making comes about. Despite the strong normative importance of politicians’ understanding of public opinion, empirical evidence on how politicians learn about these opinions in the first place is scant. Drawing on survey data collected from almost 900 incumbent politicians in five countries, this study presents unique descriptive evidence on which public opinion sources politicians deem most useful. The findings show that politicians deem direct citizen contact and information from traditional news media as the most useful sources of public opinion information, while social media cues and polls are considered much less useful. These findings matter for substantive representation, and for citizens’ feeling of being represented.