Undergraduate students in science, technology, engineering, and mathematics (STEM) programs face unique challenges to their psychological well-being, including their sense of belonging. Recent evidence suggests that beliefs about the malleability of intelligence (growth mindsets) support STEM students’ belongingness, though the mechanisms of this relationship are unclear. We propose and test a model in which students’ personal growth mindset beliefs relate to their sense of belonging by operating as a filter of environmental cues, especially those signaling instructors’ mindsets, peers’ mindsets, and the school’s trustworthiness. Across more than 3000 students in two diverse STEM contexts, we found general support for this model (mean RMSEA = 0.041; mean R2 = 39%). Perceived environmental cues fully mediated (Study 1) and partially mediated (Study 2) the total effect of personal growth mindset on belonging. In addition to model generalizability, there was meaningful heterogeneity in the results observed across contexts. These results suggest a novel filtering function of growth mindsets for belonging. Discussion centers on the factors that may account for model variability, as well as theoretical and practical implications of the findings.