Data uncertainties caused by the lack of knowledge and nature variation or randomness present vital challenges to domino effects modelling. To improve the assessment of the propagation probabilities and consequences of the domino-effect accidents, the influence of various types of uncertainties on risk assessment results needs to be investigated. However, a systematic identification of data uncertainties in domino effects has not been studied yet. In the current study, the data uncertainties in different categories (accidental, Natech, and intentional) of domino events are identified thoroughly based on historical data and literature. Meanwhile, the possible sources of the identified uncertainties are analysed by considering the environment, safety management, and operation factors. Finally, we discuss possible solutions to model uncertainties in risk assessments of domino effects. This study is a pilot study for uncertainty analysis and helps to identify the critical uncertainties that are of necessity to be considered in the domino effect risk assessments.