In social movement research, indignation features prominently as an affect that triggers protest and mobilization. Yet, scholarly accounts rarely unpack the precise ways in which indignation performs these roles, and how it transforms individuals who join mobilization. This article conceptualizes indignation as a moment of affective transformation, based on affect-theoretical insights and drawing on the empirical analysis of the Belgian yellow vest movement (BYV). Building on focus groups, participant observations, and interviews, we unpack the complex affectivity of indignation and the dynamics that underlie indignation in the context of protest and mobilization. We find that indignation enables three affective transformations: (1) it acts as a tipping point that follows from individual feelings of resentment; (2) it is a moment of affective resonance that binds individuals in affective communities, (3) it acts as affective bifurcation from the disempowered state of fear and towards the reclaiming of political power.