The empirical material and the results presented in this paper are taken from a study investigating novice primary school mathematics teachers’ professional identity development. This paper focuses on how the novice primary school mathematics teachers in the study use assessments as a tool in professional identity development. The respondents equate pupils’ results in assessments with understanding and learning and they use the assessments primarily as confirmation in identity development as mathematics teachers and not as material for planning lessons. In this paper, confirmation through assessment is illustrated by the case of Helena, one of the respondents in the study.