The study aims to examine teachers' participation in professional development (PD) in terms of gender, marital status, seniority, and content area. The causal-comparative model was used in the study. The sample of the study consists of 542 content area teachers working in K-12 schools in Turkey. Personal information form and a professional development activities scale developed by Kwakman (1999), updated by Dijkstra (2009), and adapted to Turkish by Eroglu and Özbek (2020) was used to collect the data. Descriptive statistics, t-test, and Anova were used to analyze the data. Results of the study indicated that teachers' participation in PD activities and especially collaboration activities is lower. Teachers' participation in PD activities differ significantly in terms of their gender, marital status, seniority and branches. It is thought that the low participation of teachers in PD activities is due to the limited effective professional development opportunities and the lack of support for PD in Turkey.