Public engagement has become a noticeable activity for parliaments across the world. However, we lack understanding of its role despite considerable developments in scholarly work on public engagement in the sciences and on deliberative and participatory democracy by social scientists. This article provides a framework to understand the significance of parliamentary public engagement and to evaluate its effectiveness. It explains how parliamentary public engagement has emerged because of a representational shift in who is doing the representing in parliament and in what is represented, following key societal changes. We define parliamentary public engagement, showing the importance of differentiating between the activity, its effects and broader democratic ideals. We identify information and education as the types of engagement activity most developed by parliaments, with much still to do in consultation and participation activities. The article finishes with a discussion of seven key challenges in developing and implementing effective institutional parliamentary public engagement practices.