Uncertainty touches most aspects of life and cannot be avoided, anybody is frequently presented with situations wherein a decision must be made when he/she is uncertain of exactly how to proceed. Narrow down into Information Systems (IS) field, uncertainty could be regarded as a basic but difficult problem that every HCI designer need to deal with within their design process. The purpose of this thesis is to find out how do human-computer interaction (HCI) practitioners deal with the uncertainty in their daily work. Based on this purpose, we assume that design approaches could be the methods for the designers to deal with uncertainty. There is however very few existing research on how to deal with uncertainty. In this study, we firstly categorized the uncertainty into a logical taxonomy, also ranked four design approaches by the extent of user involvement. We interviewed five HCI practitioners in different organizations that are or were working as designers. We found that most uncertainties are resulted from their customers, which can also be the most difficult to handle by them. In order to solve uncertainty, the designers need to make a good communication with others in specific situation, and some of them also proposed other practical solutions, such as “Role Play” and “Instinct Follower”. Additionally, the designers all proposed that the relationship between uncertainty and design approaches can be weak or inexistent. Interestingly, modest user involvement can be a helper for designers to solve or avoid uncertainty in the design process