Participation in research experiences and internships may improve graduation rates and persistence in science, technology, engineering, and mathematics (STEM) among undergraduates, yet very little is known about the benefits of these activities for community college students. To fill this gap, we collected survey and interview data from 43 individuals who completed the Community College Internship (CCI) at Lawrence Berkeley National Laboratory (LBNL). These 'CCI alumni' reported gains, including: connections with members of the LBNL community (95%); higher expectations of academic or career success (91%); development of critical skills (88%); and increased self-efficacy and/or confidence (84%), STEM identity (70%), and knowledge about STEM careers (65%). Of this group, 12% are graduate students, 84% have entered the STEM workforce, and 5% have entered the health workforce. We hope this work will encourage other scholars to contribute to what is known about the impact of internships at national laboratories on STEM majors.