This research, which was conducted to examine the use of punctuation marks by Turkish teachers in groups that are sub-communities of Facebook, is based on the examination of posts shared in a Facebook group established by Turkish teachers as a professional interaction community in terms of punctuation. On the basis of qualitative research methods and literature, the researchers determined criteria such as the area in which the teachers taught, the number of members of the groups, voluntary participation in the groups, the duration of the group's activity, and examined 1596 posts in accordance with the criteria. The data obtained from the examination of the posts were collected and processed with the checklists prepared by the researchers with expert approval. The data collected from the posts in the group were analyzed by thematic analysis. The findings were gathered under the themes of the use of punctuation marks, the appropriate and correct use of punctuation marks. Results were obtained from the findings presented with the themes: Group members mostly used punctuation marks, never included them at all in some posts, partially used them in some posts or used emoticons instead. When the posts are analyzed according to the appropriate and correct use of punctuation marks, punctuation errors that are not used at all, unnecessary and misused punctuation marks, the use of emoticons instead of punctuation marks, and the use of non-standard punctuation marks have been detected.