This chapter examines the individual-level relationship between citizens’ populist attitudes and their patterns of digital political engagement. While a growing body of research highlights the importance of online environments for the diffusion of populist discourse, less attention has been devoted to how citizens’ populist orientations relate to their own patterns of digital participation. The chapter explores a potential two-way relationship: whether citizens holding stronger populist attitudes are more likely to engage in political activities online, and conversely, whether individuals who participate more actively in digital political spaces display higher levels of populist sentiment. The analyses also assess whether the relationship between populist attitudes and digital behaviour varies across countries and types of participation, by comparing different forms of digital political engagement, ranging from expressive participation (such as posting or commenting on political content) to more mobilising activities (including sharing political information, organising, or participating in online campaigns). We expect to find a positive association between populist attitudes and higher levels of digital political engagement, particularly for expressive and conflict-oriented forms of participation that resonate with the anti-elitist and people-centric framing characteristic of populist discourse. By examining this potential two-way relationship, the chapter contributes to ongoing debates on whether digital political spaces primarily amplify existing populist attitudes or whether they also constitute environments where such attitudes are reinforced and normalised through patterns of political engagement.