Massive Open Online Courses (MOOCs) have provided learners unprecedented opportunities to access university level education. As a form of largely free and self-paced education, MOOCs are less formal than creditbearing university courses. It is often the case that MOOCs do not count toward a formal university qualification, and that majority learners enter MOOCs for various purposes other than specifically gaining a certificate. As a result, assessment and critical thinking, valued by universities as important learning outcomes are thought to be less relevant to MOOCs learners or designers. In the last couple of years, however, a few universities have started to design credit-bearing MOOCs as part of university programs. The aim is to encourage quality learning and outcomes that satisfy formal university assessment criteria. MOOCs designed to target particular groups of professionals for career advancement are also emerging. Both trends require a rethink of the relevance of assessment and critical thinking in MOOCs. This paper provides a case study of a MOOC targeted at health professionals, which demonstrates how self- and peer-assessment are designed to encourage critical thinking, and includes a discussion on future directions and constraints of this work-in-progress. The paper proposes that critical thinking is relevant for learning in MOOCs and that carefully designed assessment tasks are essential for developing MOOCs’ learners’ critical thinking.