Background: Community colleges have the potential to be powerful vehicles for social mobility in the United States. As institutions with tuition rates that are a fraction of the cost of four-year public and private colleges, they are a critical resource for students looking for a relatively less expensive and more flexible option to attain a degree. Their affordability makes them a particularly attractive option for students from low-income backgrounds and first-generation college students. Community colleges enroll nearly half of all postsecondary students in the U.S., and graduates who earn an associate's degree increase their earnings by more than 30 percent over a lifetime (Carnevale et al., 2014; The White House, 2015). However, for too many students, community colleges are falling short of their potential. Nationally, two-thirds of first-time, full-time, degree-seeking students who enroll in community college do not earn a degree within three years (National Center for Education Statistics, 2017). Purpose: A growing body of literature indicates that comprehensive support programs, designed to address the multiple barriers community college students face to degree attainment, can substantially improve community college students' outcomes (Weiss, Ratledge, Sommo, & Gupta, 2019; Sommo, Cullinan, Manno, Blake, & Alonzo, 2018; Evans, Kearney, Perry, & Sullivan, 2017). However, questions remain about how replicable these findings are across different contexts, management structures, and program components (Fulcher Dawson, Kearney, & Sullivan, 2020). We contribute to this literature by assessing the effectiveness of the One Million Degrees (OMD), a comprehensive support program run by a non-profit organization that supports community college students from low-income backgrounds in the Chicago area. Intervention: OMD supports students financially, academically, personally, and professionally through financial incentives, skill-building workshops, advising, and coaching. OMD students meet at least monthly with program coordinators, staff who work with scholars to set and reflect on academic and professional goals and encourage their academic and personal progress. Program coordinators work with an assigned caseload of 60-65 students and are embedded on the college campus, allowing students to meet with them on campus and enhancing Program coordinators' ability to connect students to additional resources and services through the college. Depending on a scholar's academic interests, risk for stop out, and stage in their community college journey, scholars may meet with their program coordinator as often as weekly. Students also attend monthly workshops that include meeting with a volunteer coach and participating in activities designed to build professional skills. By participating regularly in professional development programming and similar OMD events, scholars receive a performance-based stipend in addition to their last-dollar scholarships. Research Design: OMD has developed a consistently large and growing applicant pool over time, with each year's pool exceeding the number of slots available by roughly threefold. This oversubscription provides a perfect opportunity to evaluate the effectiveness of the program through a randomized controlled trial. The study utilizes a block-randomization design, where randomization is grouped within each of the seven CCC campuses and Harper College and within two applicant groups (those already enrolled at CCC or Harper and those who applied to the program prior to college enrollment). Data Collection/Analysis: Drawing on data from the National Student Clearinghouse, we estimate the effect of the program on college enrollment, persistence, and associate's degree attainment within three years of randomization. We estimate both the intent to treat (ITT) effect and the effects of treatment on the treated (TOT), using assignment to treatment as an instrument for actual program participation (Bloom, 1984; Angrist, Imbens, & Rubin.1996). Findings/Results: We find that the offer of a spot in the OMD program leads to a 4 percentage point increase in initial enrollment in college the fall after students apply to the program. Over the course of the next six academic terms, students offered a spot in the program continue to be more likely to be enrolled in college or to have earned a degree (the magnitude of these differences range between 1 and 5 percentage points). Three years after randomization, individuals offered a spot in the program have earned an associate's degree at rates that are 2 percentage points higher than their control group peers. We find no evidence of a difference between those who were offered a spot in the program and the control group in their likelihood of enrolling in a four-year college over this same period, suggesting that the program is not diverting students who would otherwise seek out a four-year degree, but also that it is not facilitating transfer to four-year institutions. For individuals who took up the offer of the program (35 percent), effects were substantially larger: a 12 percentage point increase in initial enrollment and an 8 percentage point increase in degree attainment. Interestingly, the treatment on the treated effects in our study were driven by students who applied to the program when still in high school. High school applicants were less likely to take up the offer of the program than students who were already enrolled in community college but outperformed their control group peers by a larger margin. While additional work is needed to understand these differential effects, these subgroup differences provide suggestive evidence for how limited resources could be targeted to lead to the largest impacts for students. Conclusion: These findings add promising evidence to the growing body of literature indicating that comprehensive support programs can substantially improve community college students' outcomes. By demonstrating that such programming is effective in a different context, with a different management structure (i.e., programming implemented by a non-profit provider rather than the community college itself), and with a theory of change focused on the accumulation of social capital and fostering community, these results provide optimism for the generalizability of existing positive findings about comprehensive support programs for community college students.