The current study used self-determination theory to examine the efficacy of an established and rigorous STEM enrichment program, the Summer Science Program, in promoting high school students' motivation for, and identification with, scientific research. Results of latent change analyses indicated that students' scientific research identity, intrinsic research motivation, and psychological needs for autonomy, competence, and relatedness increased significantly across two timepoints. Results of hierarchical regression analyses also indicated that satisfaction of autonomy and competence needs at a prior time point was positively associated with later intrinsic research motivation These analyses also suggested that intrinsic research motivation was both a distal and proximal predictor of scientific research identity. Overall, our findings suggest that engaging in authentic research as a high school student has the ability to promote motivation and retention in STEM and plays an important role in facilitating the socialization and assimilation of students into the broader scientific community.