This article presents a practice perspective of mathematics pedagogy and mathematics learning, by considering the interconnections between how developing a mathematics identity is bound up with the sayings, doings and relatings one experiences in classroom mathematical encounters. Broadly, mathematics education is fundamentally about stirring students into mathematical practices. In schools, doing mathematics is generally encountered in and through pedagogical practices that constitute lessons. Lessons, and the practices that compose them, create conditions for identity formation; thus one with a mathematical identity is someone who engages in mathematical practices (in everyday life and in classrooms). These practices are nuanced and site based. Considering the situatedness of lessons is an ontological view of mathematics education, and as such, offers an alternative view to the pervasive epistemological perspectives on mathematics learning, teaching and identity. To argue for a practice understanding of mathematics learning and identity development, practice theory is utilised as an analytic frame to examine empirical data from a primary school mathematics lesson. Findings delineate the ways that learning arises from being stirred into the characteristic site based practices, and mathematical identities are expressed in and, at the same time, exert pressure on the sayings, doings, and relatings encountered in lessons. From this, we argue that it is important that students engage in explicit substantive mathematics practices if they are to develop positive mathematical identities.