This article describes a longitudinal study of a social justice-oriented service-learning course at a large diverse university. The course elucidates the social causes of social problems, with poverty as a case example. Research shows that service-learning meaningfully impacts college students but that outcomes vary across courses and students, and scholars have called for greater attention to these sources of variation and mechanisms of change. Placing social justice at the center of this inquiry means focusing on a particular subset of outcomes and student characteristics. The study evaluated changes in outcomes central to social justice pedagogy, including explicit and implicit attitudes, explored whether these changes were moderated by students' social class, and tested whether attitude changes predicted civic behavior a year later. Compared to a control group (n = 172), students who took the course (n = 113) increased systemic attributions for poverty, decreased individualistic attributions, increased their awareness of class privilege, and increased their general social justice attitudes. They increased their civic action in terms of political action and general civic engagement. Implicit attitudes did not shift. Students who experienced more financial stress changed less in terms of deficit-oriented thinking but changed more in terms of system-oriented thinking. Pedagogical implications for social justice-oriented courses are discussed, including the need to consider techniques targeting deficit-oriented thinking and system-oriented thinking separately.