This study scrutinises the mechanism between uncertainty factors and supply chain quality risk (SCQR), and to examine the moderating role of supply market thinness (SMT). Drawing on agency theory and resource dependency theory, a conceptual model for the SCQR is proposed. Based on the survey data obtained from 202 managers, we use the structural equation modelling method to test our conceptual model, and the multiple group method to conduct the moderating analysis. We find that the uncertainty factors are associated with managers' perceptions of the probability and magnitude of SCQR. Moderation analysis show that the impacts of technology uncertainty and traceability uncertainty on probability of SCQR, and the impacts of technology uncertainty, testability uncertainty and product complexity on magnitude of SCQR, are moderated by SMT. The validated model provides practitioners with the direction to scrutinise the nature of SCQR, in order to establish effective practical approaches to manage it.