An important role played by tour guides on group tours is to ensure a safe and enjoyable trip; however, research focusing on their role in the field of tourism is still limited. Among tourists' behavioural intentions and satisfaction with tour guides, this study demonstrates the new role of tour guiding service quality. The data were obtained from 317 Vietnamese tourists who participated in domestic package tours. A positive correlation has been found between the tour guide's performance and the level of tourist satisfaction, as well as between tourist travel intentions and the quality of the tour guide's service. There is a substantial correlation between tourist satisfaction and tour guide performance, with service quality as an effective mediator in this relationship. The results provide insight into practical implications for tour guides to improve their capabilities and show how important tour guides are in group package tours. Tour operators need to enhance tour guide services and performance to maximize tourist satisfaction and optimistic tourist behaviour intention.