In three studies, we developed and validated the Belief-aligned Collective Action scale (BCA), a new measure of collective action that discriminates the so far confounded engagement in collective action from the ideological stance on the issue. In Studies 1a ( N = 585 Italian adult participants, 61% women) and 1b ( N = 296 British adult participants, 52% women), an Exploratory Factor Analysis identified two factors, Normative and Non-normative actions. In Study 2 ( N = 602 Italian adult participants, 50% women), a bifactor Confirmatory Factor Analysis showed an adequate fit of the two-factor structure. Across studies, the scale presents good internal reliability (as indicated by Cronbach’s α and ω total) and correlations in the predicted direction with common predictors of collective action, namely efficacy, anger, and group identity. Furthermore, Study 2 shows the generalizability of the scale to multiple topics, of which some are more relevant to left-wing people (e.g., wealth tax) and some to right-wing people (e.g., abortion). In these cases, we find no evidence for the effect of ideological variables such as political orientation and system justification. This tool allows researchers to assess collective action unbiasedly, contributing to the bridging of the ideological knowledge gap in the field of social psychology.