Mathematics education, assessment and inclusive education are far from neutral and value-free. The purpose of this chapter is twofold. First, it presents and explores ethical dilemmas in educational assessment in mathematics. The prevalence of such dilemmas resides in moments of teaching and mirrors systematic disadvantages. Secondly, teachers’ professional judgement is highlighted as crucial in resolving these dilemmas. I argue that a flexible and dialogical approach based on principles rather than fixed reasoning and rules is necessary when dealing with ethical challenges during assessment. Overall, this chapter contributes knowledge on the intersection of ethics in mathematics education and in educational assessment and offers an opportunity to explore potential ethical principles in relation to educational assessment in mathematics. This is achieved by reviewing research on ethics in mathematics and assessment, followed by a presentation of what ethical dilemmas and teachers’ professional judgement consist of during assessment. To contextualise and further knowledge within the problem area, ethical dilemmas and professional judgement are thereafter explored through the case of national assessment in mathematics in Sweden. Three fictional, but authentic, cases are presented and followed by points for discussion. These can serve to make visible values and the stance taken or needed in various contexts, on ethical dilemmas and professional judgement during assessment. Finally, the implications of ethical dilemmas to improve educational assessment in mathematics, and the role of professional judgement, are discussed.