Background: Sickness absence is a common ‘‘prescription’’ in health care in many Western countries. Despite the significance of sick-listing for the life situation of patients, physicians have limited training in how to handle sickness-certification cases and the research about sickness-certification practices is scarce. Aim: gain knowledge on physicians’ learning regarding management of sickness certification of patients in formal, informal, and non-formal learning situations, respectively, and possible changes in this from 2004 to 2008. Methods: Data from two comprehensive questionnaires to physicians in Sweden about their sickness-certification practice in 2004 (n = 7665) and 2008 (n = 36898); response rates: 71% and 61%, respectively. Answers from all the physicians ≤64 years old and who had sickness certification tasks (n = 4019 and n = 14210) were analysed. Outcome measures: ratings of importance of different types of learning situations for their sickness-certification competence. Results: Few physicians stated that formal learning situations had contributed to a large or fairly large extent to their competence in sickness certification, e.g. undergraduate studies had done that for 17%, internship for 37%, and resident training for 46%, respectively. Contacts with colleagues had been helpful for 65%. One-third was helped by training arranged by social insurance offices. There was a significant increase between 2004 and 2008 in all items related to formal and non-formal learning situations, while there were no changes regarding informal learning situations. Conclusions: This study of all physicians in Sweden shows that physicians primarily attain competence in sickness certification in their daily clinical practice; through contacts with colleagues and patients.