The aim of this thesis was to explore the cognitions (beliefs, perceptions, and knowledge) about grammar teaching that teacher of English in Swedish secondary school hold. These cognitions and their sources were explored through semi-structured interviews with four in-service teachers. The results that derive from a thematic analysis of the data, suggest that teachers’ cognitions of grammar instruction are that grammar provides a foundation and a structure to the language, and that students’ language proficiency is a key factor. Further findings reveal cognitions that support an integrated approach to incorporating both explicit and implicit methods of grammar instruction. The teachers’ own experience of grammar instruction as learners and teachers, was the most prominent source of these cognitions. This study contributes to an understanding of teacher cognitions about grammar in a Swedish context, and to how these cognitions influence their in-classroom pedagogical practices.