This study evaluated whether a career group intervention that incorporates the four sources of self-efficacy and addresses perceived career barriers is effective at improving the career decision self-efficacy and science, technology, engineering, and mathematics (STEM) self-efficacy for adolescent girls. Of the 88 girls in our study, 42 students were Latina and 46 were White, 40 were freshman, and 48 were sophomores attending the same high school. From this sample, 44 of these girls participated in a 9-week treatment group. Using repeated measures analysis of covariance with ethnicity and grade as covariates, results indicated that, compared with the control group (n = 44), participants in the treatment group improved significantly on variables of career decision self-efficacy and STEM self-efficacy and increased those gains at 3-month follow-up. The discussion focuses on implications for career counseling, limitations of the study, and future research.