This study mainly aims to identify the correlations between school principals' toxic leadership characteristics and teachers' perceptions of mobbing. Beside its fundamental purpose, this study also aims to identify the levels of school principals' toxic leadership characteristics and of teachers' mobbing perception and whether or not those levels differ according to demographic and occupational properties. The study uses the relational survey model and quantitative design. The sample was composed of 455 teachers teaching in schools in Çanakkale city centre and in the county of Çan in 2023-2024 academic year. The research data were collected with the Demographic Information Form, Mobbing Scale and Toxic Leadership Scale. Percentage analysis, frequency analysis, regression analysis, correlation analysis, Mann Whitney-U test, Shapiro-Wilk test, Kolmogrov-Smirnow test and Kruskal Wallis-H test were used in analysing the data. As a result, teachers' perceptions of school principals' toxic leadership characteristics and their perceptions of mobbing were generally found to be at medium level. In addition to that, teachers' perceptions of toxic leadership differed significantly according to gender, level of education and school where they taught. On the other hand, positive and significant correlations were found between principals' toxic leadership characteristics and teachers' perceptions of mobbing. As a result, school principals' behaviours and performance can be monitored and evaluated, and administrators can be offered training by giving feedback in relation to their toxic leadership and mobbing behaviours.