Using social-cognitive career theory, we identified the experiential sources of learning that contribute to research self-efficacy beliefs, outcome expectations, and science identity for culturally diverse undergraduate students in science, technology, engineering, and math (i.e., STEM) majors. We examined group differences by race/ethnicity and gender to investigate potential cultural variations in a model to explain students' research career intentions. Using a sample of 688 undergraduate students, we ran a series of path models testing the relationships between the experiential sources, research self-efficacy beliefs, outcome expectations, and science identity to research career intentions. Findings were largely consistent with our hypotheses in that research self-efficacy and outcome expectancies were directly and positively associated with research career intentions and the associations of the experiential sources to intentions were mediated via self-efficacy. Science identity contributed significant though modest variance to research career intentions indirectly via its positive association with outcome expectations. Science identity also partially mediated the efficacy-outcome expectancies path. The experiential sources of learning were associated in expected directions to research self-efficacy with 3 of the sources emerging as significantly correlated with science identity. An unexpected direct relationship from vicarious learning to intentions was observed. In testing for group differences by race/ethnicity and gender in subsamples of Black/African American and Latino/a students, we found that the hypothesized model incorporating science identity was supported, and most paths did not vary significantly across four Race/Ethnicity × Gender groups, except for 3 paths. Research and practice implications of the findings for supporting research career intentions of culturally diverse undergraduate students are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).