In contrast with the field of second language acquisition (SLA), where until recently sociocultural concerns were largely unaddressed (Block, 2007), identity has always been at the core of heritage language (HL) education. The present article highlights this often overlooked history and presents action research centering on a Spanish critical service-learning program stressing identity and social activism in HL education. The article begins with an examination of the constructs of identity, agency, and advocacy in Spanish HL education and critical pedagogy. Stressing that critical pedagogy seeks not only to promote agency but also to contribute to social justice outside of the classroom, we provide an overview of our critical service-learning program melding university HL education with community language activism. The program builds upon HL speakers' classroom-based learning of critical language awareness by providing community-based opportunities to enact and strengthen identities as language experts and to contribute to positive social change. Next, we present and analyze qualitative data gathered in order to investigate the emergence of expert and activist identities among program participants who worked to counteract school-based subordination of Spanish by running an after-school Spanish class for HL speakers at a local elementary school.