Improving the state of science education in the United States has become a national priority. One response to this problem has been the implementation of STEM enrichment programs designed to increase the number of students that enter graduate programs in science. Current research indicates enrichment programs have positive effects for student performance, degree completion, interest in science and graduate enrollment. Moreover, research suggests that beyond improving performance in STEM, and providing access to research experience and faculty mentoring, enrichment programs may also increase the degree to which students identify as scientists. However, researchers investigating the role of science identity on student outcomes have focused primarily on subjective outcomes, leaving a critical question of whether science identity also influences objective outcomes such as whether students attend graduate school. Using identity theory, this study addresses this issue by investigating science identity as a mechanism linking enrichment program participation to matriculation into graduate science programs. Quantitative results from a panel study of 694 students indicate that science identity salience, along with research experience and college GPA, mediate the effect of enrichment program participation on graduate school matriculation. Further, results indicate that although the social psychological process by which science identity salience develops operates independently from student GPA, science identity amplifies the effect of achievement on graduate school matriculation. These results indicate that policies seeking to increase the efficacy of enrichment programs and increase representation in STEM graduate programs should be sensitive to the social and academic aspects of STEM education.