The importance of the role of peer and self-assessment in developing formative and sustainable assessment practice in higher education is increasingly becoming evident. PeerWise is an online software tool that engages students in contributing to their own and others' learning by authoring, answering and providing feedback on multiple choice questions. Using a mixed methods approach, 20 students responded to discussion questions and an online survey about their perceptions of using PeerWise compared to online quizzes as part of the blended delivery of a postgraduate psychology unit. Students considered both authoring and answering questions in PeerWise to equally benefit their learning. Answering questions in PeerWise was perceived to be more helpful for learning than questions on a Moodle quiz. This advantage was evident across more complex cognitive skills, understanding, applying, evaluating and creating information, although only significant for facilitating understanding. PeerWise and online quizzes were seen to be equally helpful in facilitating recall. Despite the perceived benefits of PeerWise, students preferred quiz questions to be set by an expert if used as recognition of progress. Introducing PeerWise was effective in promoting engagement with peers; however, refinements to the model should focus on increasing student confidence in their own and peers' capabilities.