Spontaneous self-affirmation refers to the natural tendency to reflect on one's strengths, values, or social relationships when encountering everyday psychological threats. Previous research has identified spontaneous self-affirmation as a personal resource linked to adaptive outcomes, including enhanced well-being. The present study aimed to extend this literature by examining whether spontaneous self-affirmation is associated with positive body perceptions and eating attitudes among university students. Specifically, it investigated the associations among spontaneous self-affirmation, body satisfaction, and negative eating attitudes, as well as the mediating role of body satisfaction in the relationship between spontaneous self-affirmation and negative eating attitudes. Participants were 285 university students (185 women, 100 men). They completed self-report measures assessing spontaneous self-affirmation, body satisfaction, and negative eating attitudes. Results revealed that spontaneous self-affirmation was associated with increased body satisfaction, whereas body satisfaction was related to decreased negative eating attitudes. Moreover, mediation analysis indicated that body satisfaction mediated the association between spontaneous self-affirmation and negative eating attitudes. Specifically, higher levels of spontaneous self-affirmation were associated with greater body satisfaction, which, in turn, was linked to fewer negative eating attitudes. In conclusion, these findings highlight the potential of spontaneous self-affirmation as a psychological resource related to more positive body perceptions and healthier eating attitudes among young adults.