This presentation discusses the relevance of investigating multilingual mathematics teachers’ professional identity in multilingual mathematics contexts. Research on mathematics education still lacks cases of teachers with a diverse linguistic background more than the language of instruction. A participatory view of identity will be followed in order to provide empirical results on how is to be and become a multilingual mathematics teacher in multilingual contexts. The theoretical framework of Patterns of Participation will be adapted. An ethnographic longitudinal study of three teachers in lower secondary mathematics level in Sweden is proposed. The data will be generated from teachers observations in classroom and interviews about their educational and professional background, as well as instances of classroom interaction with students.