Teachers' effective use of mathematical language in teaching mathematics appears as a factor that certainly influences students' insight into the lesson. This research aims to investigate the views of primary school teacher nominees about the mathematical language applied in mathematics lessons and to make some recommendations for the effective use of mathematical language. This research has been organized using phenomenology research design, one of the qualitative research designs. The study group of this research consists of 12 teacher candidates who endure their education in the Department of Primary Education. The semi-structured interviews were conducted face-to-face. The data obtained was considered by descriptive analysis technique. In this context, the participants stated the mathematical language idea as a concept, symbol, graph figure, sign, number, and term. Besides, the participants listed the factors affecting the effective use of mathematical language as difficult, daily life language, time, curriculum, attitude, incomplete, and application. Finally, the participants made some recommendations such as it should be included in the curriculum, activities should be prepared, visual materials should be used, emphasis should be placed on undergraduate education, and simple, clear, and understandable language should be used to increase the effective use of mathematical language. As a result, teachers need to have the competencies to use mathematical language effectively, as it will increase the mathematical achievements of students. Hence, both pre-service and in-service training should be provided to prospective teachers and teachers to enable them to use the mathematical language effectively.