The social turn in mathematics education has implied that researchers wish to include collaborative and social aspects when accounting for students’ learning in mathematics. To accomplish this task many theoretical frameworks have been introduced, some of these also used in the field of mathematics education. Several publications produced by Swedish researchers in mathematics education have used the theory of contextualization and the related analytical principles of Intentional analysis to conceptualize and analyze mathematical teaching and learning. The theory of contextualization is situated in constructivist ontological and epistemological principles and is operationalized to include conceptual, situational, and cultural aspects of students’ conceptions of a given task. In this chapter we elaborate on the theory of contextualization and how it may be used to study mathematics learning and teaching by bringing together five examples of students´ learning of mathematics in compulsory school and higher education previously separately presented in international publications in mathematics education.