PurposeThis study aims to provide service managers and researchers with a deeper understanding of the direct on-site interactions taking place between customers.Design/methodology/approachUsing the Critical Incident Technique (CIT), 284 incidents are analysed to develop a typology of how service customers experience direct on-site CCI.FindingsThe research reveals a wide range of CCI. A typology consisting of nine distinct categories of CCI emerged: (1) shared use space, (2) assigned space and possessions, (3) information provision, (4) assistance, (5) social conversations, (6) disrespectful attitude, (7) queuing discipline, (8) transaction efficiency and (9) undesired customers and ‘camouflaged customers’. These categories can accommodate a multitude of customer behaviours that impact, negatively or positively, on the service experience of other customers.Research limitations/implicationsFuture studies could be conducted following a more inclusive research design capable of gaining CCI insights from employees and managers.Practical implicationsPractitioners can use the typology to systematically identify the full range of specific CCI behaviours affecting their businesses. It also assists them in the analysis and understanding of individual C2C (customer-to-customer) interactions. For academics the typology makes available a comprehensive framework to guide future research into CCI.Originality/valueThe study constitutes the first systematic attempt to classify direct on-site CCI across a wide range of services. The typology, unrestricted by any single-industry bias, is robust and conceptually broad, and therefore highly portable across service industries.