We examined implications of evaluative threat on the ability to regulate emotions for first-time college freshmen completing Science, Technology, Engineering, and Math (STEM) majors (N ϭ 432). Students completed the Evaluative Threat in STEM Scale (Ahlqvist, London, & Rosenthal, 2013) and the Difficulties in Emotion Regulation Scale (DERS; Gratz & Roemer, 2004) at six intervals. Cross-sectional and longitudinal measurement invariance was supported. Women reported greater evaluative threat than men, but they did not differ from men in difficulties regulating emotion. Both constructs showed moderate relative stability over time. Using latent change score analyses, significant positive deceleration change patterns indicated that four of the emotion regulation difficulties (Lack of Emotional Awareness, Lack of Emotional Clarity, Impulse Control Difficulties, and Nonacceptance of Emotional Responses) and evaluative threat tended to increase (worsen) over the year, but the increases also slowed (i.e., plateaued) over time. Compared with men, women initially reported higher evaluative threat than men did, but these differences decreased over the year, as women decelerated more quickly than men did. In terms of cross-coupling effects, we found that evaluative threat was associated with subsequent difficulty in identifying strategies to cope with unpleasant emotions. There were no cross-coupling effects for emotion regulation predicting subsequent change in evaluative threat. Gender moderated the Evaluative Threat-to-DERS coupling effects for Lack of Emotional Clarity, Difficulties in Goal-Directed Behavior, and Nonacceptance of Emotional Responses. We discuss implications of evaluative threat for depleting coping resources and some potential psychoeducational and preventive interventions to support students in STEM majors. Public Significance StatementThis study asked freshmen science, technology, engineering, and math (STEM) students to report their levels of evaluation threat (stress) and difficulties coping with emotions for the first year in their major. Women had higher levels of evaluation threat (stress) than men in STEM majors. For women and men, higher threat led to fewer strategies to cope with unpleasant feelings. Changes in other emotion regulation difficulties were affected differently by evaluation threat for women and men. Several findings suggested that the students might benefit from stress management interventions early in their time at the university.