The aim of this study is to examine the relationship between school principals' personality traits and teachers' psychological well-being. The research is designed in a relational survey model. The population of the study consisted of teachers working in schools in the Dalaman district of Muğla province during the 2023-2024 academic year. The sample of the study consists of 405 teachers selected from this population using the disproportionate cluster sampling technique. The data were collected using the 'Big Five Personality Scale' and the 'Psychological Well-Being Scale.' Descriptive statistics, t-test, one-way analysis of variance (ANOVA), Pearson correlation analysis, and regression analysis were used to analyze the data. The results obtained from the study show that teachers exhibit a high level of psychological well-being. While teachers' psychological well-being differs according to their gender and the school level they work at, it does not differ according to their seniority. School principals exhibit high levels of conscientiousness and extraversion, moderate levels of agreeableness, openness to new experiences, and neuroticism personality traits. The extraversion personality trait of school principals is a significant predictor of teachers' psychological well-being.