<p>Several studies have examined the effects of polarization on election turnout, but the consequences for other forms of participation have remained unexplored. I draw on research on the mechanisms mobilizing non-electoral participation to examine the effects of change in polarization on this form of political engagement, distinguishing institutional and noninstitutional participation. Building on the literatures on respective determinants of both types of participation, I expect polarization to have a positive effect on both types of participation, but I expect that the effect is stronger in the case of noninstitutional polarization. I present longitudinal analyses of the effect of system-level affective and ideological polarization on non-electoral participation as well as protest mobilization in 22 European countries in the period 2002–2019. Results point to a positive effect of polarization on protest participation and mobilization, but show no evidence of an effect of polarization on institutional participation.</p>