Humans have the ability to describe and discuss language, which is known as having a metalanguage. In the Swedish educational system, students are expected to develop a metalanguage in all subjects to be able to communicate about the various subjects. The syllabus for the subject of Swedish at upper secondary school states that students should develop knowledge about the Swedish language and the ability to talk about and analyze language. Even though previous research on the use of metalanguage is inconclusive, there is evidence that suggest that the use of a grammatical metalanguage within a functional grammatical discourse can be beneficial for students’ development in writing. Studies have shown that the subject of Swedish generally use a more colloquial language, which is why this study aimed to investigate teachers’ and students’ use of metalanguage in terms of grammatical terminology. A combination of ethnographic method and discourse analysis was used, and three teachers and their students were observed over a period of approximately two months. Notes from the observations as well as teacher feedback in students’ texts, assignment instructions and students’ written tasks were collected and analyzed through grammatical discourses and a model for metalanguage use. The results show that mainly teachers use grammatical metalanguage while students only use such meta-language when instructed by the teacher to do so. Furthermore, the use of grammatical meta-language varies based on context, but is more frequent when grammar poses as study object. The teachers use grammatical metalanguage mainly within a prescriptive and descriptive grammatical discourse, but there are instances of usage within a functional discourse. The students’ use of grammatical metalanguage is characterized by a lack of understanding of grammatical terminology, and they struggle to make clear connections between the term and its meaning in written language.