There is a widespread interest in doctoral supervision, yet novice doctoral co-supervisors' experiences remain understudied. The aim of this qualitative study is to explore how supervision culture and practice are experienced by novices. This thematic analysis is based on focus groups and in-depth interviews with 23 novice co-supervisors from two Swedish research-intensive universities. The study reveals three dimensions related to the challenging experience of the "supervision culture," namely closedness, dependence and competition. Moreover, the analysis proves that "co-supervisors' practices" are embedded within the 'hidden curriculum', here defined as the unplanned and implicit support outside formal meetings and activities. Novice co-supervisors bridge the gap between main supervisors and doctoral students and make the path to the doctoral degree smoother when engaging in emotional, intellectual, practical and mediation support. This study has practical implications and suggests improvements for co-supervision that would also benefit the doctoral students.