Purpose: The purpose of this paper is to identify the key elements of professional identity in service work in order to provide more in-depth theoretical explanations as to why service workers do as they do while co-creating service. Design/methodology/approach: This study takes a multi-perspective on professional identity, i.e. using both an employee and a customer perspective, arguing that the phenomenon mainly consists of what these interactants jointly do during the service interaction and of the meanings that are attributed to it. The authors draw on a detailed empirical study of professionals working at a customer centre. Methodologically, the study is based on practice theory, which helps us to illuminate and analyse both the micro practices and the meaning attributed to the professional identity of service workers. Findings: The key elements of professional identity in service work are outlined within a framework that describes and explains three different facets of the service workers’ professional identity, i.e. as a core (i.e. individual resources, cognitive understanding, interaction), as conditions (i.e. service prerequisites), and as contour (i.e. demeanour and functions). Research limitations/implications: The findings are based on an empirical data set from a public transport customer centre. As the results are limited to one context, they do not provide statistical generalizability. Although limited to one service industry, the findings may still be of high relevance to a wide range of service organisations. Practical implications: The study shows the significance of managers not just talking about the importance of being service-minded; more exactly, a wide range of service prerequisites, beyond cognitive understanding, needs to be in place. It is crucial that service workers are given the time to develop their contextual knowledge of their customers, and of other parts of the service organisation. Originality/value: This study offers original empirical contributions concerning the key elements of professional identity. An alternative conceptualization of professional identity is provided, through which the paper adds to service research, explaining more specifically what kinds of knowledge and skills are in use during the co-creation of services.