Decades of scholarship on teaching and learning affirm the benefits of public service internships on student learning outcomes. Studies emphasize how hands-on fieldwork can increase students' substantive knowledge, political efficacy, trust in government, and civic participation, among other factors. However, most articles treat internships equally without accounting for the variation in the institutionalization of experiential-learning programs within and across universities. We theorize that more structured internship programs (e.g., more student credits, intentionally designed curricula, additional faculty guidance) yield larger impacts on learning objectives centered on civic culture and education. We test this theory by analyzing three years of student data from two public universities' fieldwork programs. We compare pretest and posttest survey results from undergraduates (1) participating in structured public service internship programs run in a state capital, (2) participating in internships pursued independently, and (3) majoring in a social science degree but having yet to complete an internship. We find that students pursuing a solo internship or via a structured program begin and end with higher political knowledge, efficacy, civic engagement, and related attitudes than the control group. We also find the more systematized an internship experience, the bigger the effect on key student learning outcomes. These results underscore how political science departments can fortify civic culture through more structured public service internship programs.