This paper investigates uncertainty perception as a general driver of individual design activity. An observation based protocol study is used to explore the interaction between uncertainty perception and three core actions connected in design activity: information action, knowledge sharing action, and representation action. We bring together prior works on uncertainty perception in the design and management literatures to derive three contributions. First, we describe how uncertainty perception is associated with activity progression, linking all three core actions. Second, we identify characteristic patterns of interaction between uncertainty perception and activity. Third, we decompose uncertainty perception to further explain its role in driving design activity. This extends prior research on design activity, and supports a number of theoretical and empirical implications.