The present studies aimed to advance the measurement and understanding of microaffirmation kindness cues and assessed how they related to historically underrepresented (HU) and historically overrepresented (HO) undergraduate student persistence in science-related career pathways. Study 1 developed and tested the dimensionality of a new Microaffirmations Scale. Study 2 confirmed the two-factor structure of the Microaffirmations Scale and demonstrated that the scale possessed measurement invariance across HU and HO students. Further, the scale was administered as part of a longitudinal design spanning 9 months, with results showing that students' reported microaffirmations did not directly predict higher intentions to persist in science-related career pathways 9 months later. However, scientific self-efficacy and identity, measures of student integration into the science community, mediated this relationship. Overall, our results demonstrated that microaffirmations can be measured in an academic context and that these experiences have predictive value when they increase students' integration into their science communities, ultimately resulting in greater intentions to persist 9 months later. Researchers and practitioners can use the Microaffirmations Scale for future investigations to increase understanding of the positive contextual factors that can ultimately help reduce persistence gaps in science, technology, engineering, and mathematics degree attainment.