The current study aims to focus on the relationship between school principals' quantum leadership behaviours and teachers' psychological capital levels. The target population of the study consists of 462 teachers working at public schools in Sapanca district of Sakarya in 2020-2021 academic year. The sample of the research consists of 224 teachers selected through simple random sampling. "Scale on the Quantum Leadership Behaviours of School Principals" developed by Erçetin, Potas, Açikalin and Turan (2017) and "Psychological Capital Scale" adapted by Çetin and Basim (2012) were used to gather data. Descriptive statistics and non parametric methods were used to analyze the data. According to the findings, the level of school principals' quantum leadership behaviours is "frequent" and the level of teachers' psychological capital is "totally agree". There is no significant difference between teachers' perceptions on the school principals' quantum leadership behaviours according to "gender, educational background, professional seniority, educational stage and duration of working with the current principals". Teachers' perceptions on the level of teachers' psychological capital don't differ significantly according to "gender, educational background, professional seniority and duration of working with the current principals" but there is a significant difference between high school and primary school teachers in favour of primary school teachers according to "educational stage". Moreover, there is a moderate, positive and statistically significant relationship between school principals' quantum leadership behaviours and teachers' psychological capital levels.