Over the past decade, co-supervision of PhD candidates has become increasingly common across the disciplines. However, co-supervision has been explored previously primarily from the candidates' viewpoint and in small-scale qualitative studies. We have extended the research by examining co-supervisory experience from the supervisor's perspective, and by exploring the influences of co-supervision for supervisory competencies and the occupational wellbeing with a large-scale quantitative survey. 561 supervisors participated in the study. The data were analysed with statistical methods. The results showed that having a supervisory team has become the dominant from of supervision across the disciplines. Furthermore, the frequency of engaging in co-supervision was related to supervisor's occupational wellbeing, but the association was not straightforward. Having experience in co-supervision seemed to contribute to feeling more confident with one's supervisory competencies. The findings imply that the development of well-functioning co-supervision practices can enhance supervisors' competencies and occupational wellbeing alongside promoting PhD candidates' studying.