This study examines the activities of a local group of Critical Mass (cycling) enthusiasts to inquire into the aspirations for their participation. The research employs a multimethod, ethnographic approach to explicate the identity work associated with the enthusiasts’ involvement in the phenomenon and local activism. Drawing from sociological perspectives on identity convergence and identity formation processes, the analysis finds that the core group of participants assume heavy leadership roles in Critical Mass in part to enhance their personal identity as political activists. The article also details the form and function of Critical Mass as a type of cultural movement to contextualize the analysis. The article seeks to contribute to the literature on identity convergence, suggesting some collective action participants seek opportunities to enact and affirm collective identities important to their personal self-conception. Implications of the research for the study of identity formation processes within the context of cultural movements are discussed.