Sociologists have debated whether and how medical trainees are socialised to deal with uncertainty for decades. Recent changes in the structure of medical education, however, have likely affected the ways that resident physicians learn to manage uncertainty. Through ethnographic case studies of academic medical centres in Switzerland and the United States, this article provides new insights into the processes through which residents learnt to manage uncertainty. These processes included working under supervision, developing relationships of trust with supervisors and gaining autonomy to practise independently. As a result, residents developed different attitudes towards uncertainty. Residents at the Swiss medical centre tended to develop a more pragmatic attitude and viewed uncertainty as something to be addressed and controlled. On the other hand, residents at the American medical centre tended to develop an acceptive attitude towards uncertainty. More broadly, residents learnt to reproduce their supervisors' attitudes towards uncertainty. This article therefore provides new perspectives on continuity and the reproduction of social phenomena in medical education.