The stigma faced by gender and sexual minorities varies across countries. How does stigma relate to collective action for social change? We propose a curvilinear link (i.e., an inverted U-curve) between stigma and collective action such that increased stigma is associated with increased collective action up to a point, beyond which, increased stigma is associated with reduced collective action. Using Bayesian inference with a sample of over 3,000 lesbian, gay, bisexual, transgender, intersex, and queer (LGBTIQ+) individuals across 25 countries, analyses showed that at the between-country level (but not at the within-country level), there was preliminary evidence of a curvilinear effect. There was also an indirect effect of institutional stigma on collective action outcomes via perceived stigma, suggesting that structural-level factors can trickle down to shape individuals’ social change intentions and behaviours. These findings raise the importance of reconsidering the assumption of linearity between stigma and collective action.