Engaging and retaining undergraduate students in science, technology, engineering, and math (STEM) fields is essential for the future workforce in the USA. Building off a growing body of research which explores how intelligence beliefs impact psychosocial variables of STEM engagement (e.g. STEM self-efficacy, sense of belonging), the current research included 523 undergraduate STEM majors. Participants answered a series of questions about their self-intelligence beliefs and perceived intelligence beliefs of their professors. Findings from a series of mediation analyses showed that participants' perception of their professors' incremental beliefs predicted variables associated with STEM engagement and retention (STEM interest, STEM self-efficacy, sense of belonging in STEM, and grit) through participants' self-incremental beliefs. These findings highlight the important roles that academic environments (e.g. perceived intelligence beliefs of one's professors) and one's intelligence beliefs play in STEM engagement. Future directions and implications are discussed.