Purpose: The purpose of this paper is to understand, from principals' points of view, how a teacher registration reform is enacted by examining the potential changes in the relationships between principals and newly qualified teachers (NQTs). The reform entailed principals performing an aptitude assessment of new teachers in their probationary year. Design/methodology/approach: Semi-structured interviews were conducted with five principals from two Swedish municipalities on three occasions in one academic year. A third follow-up interview was conducted one year later with four of the principals, the fifth no longer being in post. Findings: The assessment appears to be downplayed by the principals, whereas the supportive dimension and the facilitation of NQTs' professional development seem to be acknowledged and made explicit. For some of the principals, their creative translation of the reform's intentions transformed these relations and strengthened their leadership. Research limitations/implications: The study is small-scale and was carried out in a specific period of policy implementation from the principals' perspectives. Future studies would benefit from involving both principals' and teachers' perspectives. Practical implications: Policymakers appear to have underestimated the structural aspects of the reform, even though in general the reform enactments had some kind of positive effect on these relations. Social implications: For some principals, their creative translation of the reform's intentions transformed relations and strengthened their leadership. Originality/value: The data are from a unique period when a reform was implemented and later partly withdrawn. The study deepens the understanding on how principals tries to enact and balance their roles as evaluators of NQTs and pedagogical and instructional leaders.