This study examined how students from historically marginalized identity groups (i.e., Black and Latinx, females, and first-generation college students) engage momentarily in a school-based task. We explored how John Henryism, defined as effortful, active coping as a response to environmental stress, and growth and fixed mindset mediate the relationship between identity groups and momentary engagement outcomes (i.e., positive/negative emotions and cognitive engagement). Findings from two structural equation models--one including John Henryism as a mediating latent construct and one without--demonstrated that only John Henryism mediated the relationship between historically underrepresented groups and positive momentary engagement (i.e., increased cognitive engagement and positive emotions, while lowering negative emotions) while growth mindset did not. These findings suggest that John Henryism and growth mindset may work together to buffer environmental stressors that affect historically underrepresented students' academic success.