This article explores the sociopolitical development (SPD) of youth activists involved in climate justice and gun violence prevention movements. Interviews with 52 youth members of five different youth‐led activist organizations and follow‐up surveys supplied the data. We found that involvement in youth‐led activist organizations facilitates a particular kind of SPD we term “intersectional politicization.” Intersectional politicization involves critical intersectional reflection paired with critical intersectional action. Critical intersectional reflection entails analysis of how marginalized populations are impacted by particular social problems and how various social issues and forces of oppression interconnect. Critical intersectional action consists of participating actively in multiple movements or activist organizations to address distinct issues simultaneously. Intersectional politicization is fostered through organizational trainings and programming, collaborative work with other organizations, dialog with fellow activists, and online activist content. Intersectional politicization raises new considerations for research on critical consciousness and youth SPD.