The retention disparities in undergraduate degree attainment are a persistent problem within the United States, especially for Black, Indigenous, People of Color (BIPOC), first-generation and low-income students, and women (referred to as marginalized groups in STEM [MGS] hereafter) pursuing STEM degrees. The following exploratory article illustrates how a program called STEMentors based in the Department of Chemistry has led to positive outcomes for MGS students taking general chemistry in 2021-2022. The goal of the article is to highlight how this program serves as an example for other universities to create and implement a similar model to support MGS students. The STEMentors program is a supplemental instruction opportunity aimed to mentor MGS students to further support them with the academic skills, study strategies, and content knowledge needed to be successful in first-year chemistry through a peer-led tutoring learning model. Qualitatively, the program draws from aggregated postsurvey data (N = 50) and student interview data (N = 5) to elucidate how students perceived their academic readiness and community building as a function of belonging. Implications suggest supplemental instruction programs like STEMentors are effective in helping students improve their belonging as a function of academic readiness and community building. Thus, continued research should work toward developing similar supplemental instruction programs across STEM courses.