This research examines the role of Supplemental Instruction in assisting students at a small Hispanic-Serving Institution (HSI) in the Southwest United States to improve their final grades in a required statistics course for criminal justice majors. Data collected over three semesters were analyzed using multivariate regression to test if participation in Supplemental Instruction moderates the relationship between race, ethnicity, and final grades earned, with Latinx students and students from other historically underrepresented racial and ethnic groups especially benefitting from SI participation. We find positive interactions for race, ethnicity, and final grades; however, the interaction term is only statistically significant for students from other, non-Latinx underrepresented racial and ethnic groups. These students attended SI most frequently, derived the most benefits from their participation, and were also notably the most underrepresented in the institution and the course. We go on to discuss evidence-based recommendations that SI and other collaborative learning programs may consider if their goal is to move toward servingness by improving equity in performance and academic success outcomes across students from diverse backgrounds.