Opportunism is a common issue in buyer-supplier relationships. However, while many existing studies investigate interfirm-level opportunism, a few studies investigate individual-level opportunism, and currently, there has been a call for further research on how to manage individual-level opportunism. Thus, to contribute to the current research trend, this study examines factors influencing individual supplier agent opportunism. Data was collected by an interview-based exploratory study of 24 practitioners, from December 2018 and March 2020. The results from data coding and analysis identify two groups of important factors in managing supplier agent opportunism: 1) organisational factors group includes buyer-supplier companies’ long-term relationships, buyer companies’ dependence, co-worker support for buyer agent, job demands for supplier agent; 2) individual factors group includes close relationships between buyer agent and supplier agent, buyer agents’ purchasing knowledge, communication skills, and honesty in negotiation.