This article examines the relationship between formal ideologies and processes of collective identity construction across two key waves of mobilisation of pro-asylum-seeker groups in Ireland, namely radical anti-racism and the multicultural support group. In each period, a formal ideological stance delimited the scope of actions available to members. In examining the interplay between collective identity and ideology, the actions and trajectories of individual social movement organisations (SMOs) and the movement at large can be better understood. Processes of collective identity construction facilitated SMO members in creating conditional senses of ‘weness’. In instances, these challenged formal ideologies with differing results. In the case of radical anti-racism, it created a reformist/radical division among members. In the multicultural support group, it created a reformist/non-reformist division. These cleavages are crucial to understanding how the movement progressed over time. Collective identity work is understood as a means through which individuals can challenge or reinforce formal ideologies, thus playing a crucial role in the trajectories of the SMOs examined and their repertoire of actions.