The purpose of this study is to carry out a content analysis about the studies on teachers' professional development and to determine the tendencies in these studies. Within this scope, 60 studies that were registered to Turkish National Thesis Centre and ProQuest database between the years 2005-2015 were examined. Of the 60 studies, 37 of them were doctoral dissertations while 23 were written as master's theses. As part of the content analysis, the related studies were coded and categorized on a separate file according to certain variables. These variables were publication type, publication language, the year, field of research, research design, data collection tools, data analysis, the number of analyses, participant type, number of participants, average participant size, areas of study, findings, and recommendations. The data were analyzed through SPSS 20.0 software program. The results were presented as frequencies and percentages in a descriptive way. The findings of the current study indicated that the number of doctoral dissertations was more than the master theses and the 82 % of the studies were written in English. Of the 60 studies on teachers' professional development, 20 of them were conducted in the years 2013-2014 and the most frequently used research design was qualitative research design. The most commonly used data collection technique was the interview while survey was the most frequently used data collection tool. The most frequently used sample type was teacher and the most frequently encountered sample size was 0-30. On average, 78 participants took part in the studies while the minimum number was one and the maximum number was 1341. Lastly, the most frequently studied area was professional learning communities with a total number of 16 studies.