This paper draws on staff and student consultations conducted during the development of Student Minds' University Mental Health Charter to identify five key tensions which can arise in assessment design and strategy when seeking to balance the wellbeing of students with pedagogical, practical and policy considerations. It highlights the need to acknowledge the pressures of assessment on staff wellbeing as well as students. The particular tensions explored include the need to balance challenge against the psychological threats this can entail; the varying impacts of traditional and novel forms of assessment; the differing demands of collaborative and individual work; the tensions between ideal strategies and those which are practically feasible; and the ways in which feedback is given (as a constructive learning tool) and received (often as a psychological threat). These tensions can provide a valuable point of reflection for educators who need to critically and proactively navigate these conflicts within their own assessment design and practices, as part of a wider whole university approach to promoting student wellbeing.