The current study examined how participation in an undergraduate research experience (URE) that provides a counterspace affects sociocognitive factors (science self-efficacy, science identity, and academic self-concept) and how they, in turn, may shape science career intention in a sample of STEM undergraduate students. STEM majors from a public university in California completed surveys from 2017 to 2020 and rated their science identity, science self-efficacy, academic self-concept, and their intention to pursue a science-related research career. Structural equation modeling shows that URE participants reported higher (a) science self-efficacy, (b) science identity, and (c) academic self-concept relative to students who did not participate in the URE. While there was an indirect effect of science self-efficacy on science career intention mediated by science identity, higher science self-efficacy and academic self-concept were negatively associated with the intention to pursue a science career. MANOVA results suggest that URE participants fared better than non-URE students in all outcomes across all sub-groups. These results highlight the importance of an identity-focused UREs and the counterspace it fosters among STEM majors from diverse backgrounds.