Purpose – This paper aims to explore how novice doctoral co-supervisors promote PhD students’ well-being. It provides a more nuanced understanding of how early-career academics engage with the relational and emotionally complex nature of co-supervision. Design/methodology/approach – The qualitative study draws on 25 in-depth interviews with novice co-supervisors at two research-intensive universities in Sweden. Data were analysed using reflexive thematic analysis within a symbolic interactionist framework. Findings – The results reveal that novice co-supervisors promote PhD students’ well-being. Drawing on their social expertise, they contribute by reducing social isolation, structuring the supervisory process, fostering scholarly independence and creating opportunities for open dialogue about well-being. Practical implications – This study can serve as a basis for discussions about novice co-supervisory roles and their involvement in PhD student well-being. It also highlights that new supervisors may require support structures at multiple levels – clear policies, structured team induction, training, mentoring and, above all, a supportive supervisory culture. Originality/value – The originality of this study lies in its close look at the role of novice doctoral co-supervisors. Using a symbolic interactionist lens, it shows how everyday relational practices can become part of the structure of supervision. Its value lies in highlighting how novice co-supervisors help shift supervision towards a more supportive and caring culture.