The extension of common acts and competencies shared among medical specialties can be considered a strategy to improve access to specialized care in health systems. However, initiatives in this direction run into continuous disputes over exclusive and private practices. The present study investigates the exclusive versus expanded practice around medical specialties among physicians in Brazil. It was a cross-sectional study based on data collected from official Brazilian State and medical entities records (2015 and 2021). Were carried out: (i) identification of the prevalence of physicians with expanded activities in the scope of more than one specialty and, on the contrary, exclusive to a single specialty; (ii) analysis of differences according to individual attributes and relative to the professional practice locations; and (iii) binomial logistic regression for analysis of factors associated with extended versus exclusive practice. About 36% of Brazilian doctors had an expanded practice around medical specialties in 2021 - a small reduction compared to 37.9% in 2015. The professionals with the greatest tendency towards expanded scopes are those who work in surgical, cardiology, and oncology specialties, associated with working in a small, remote municipality with a shortage of doctors, where professionals tend to travel to provide care, but also in environments with greater clinical diversity, such as hospitals. Exclusivity occurs more frequently in Ophthalmology, Psychiatry, Otorhinolaryngology, Dermatology, and others, and is associated with having a corresponding specialist title, being female, working in a private establishment, and working in large urban centers. The results point to a significant extension of physicians’ scope of practice between medical specialties in Brazil, despite the resistance of the model characterized by private and exclusive acts. Therefore, possibilities of migrating to a model characterized by shared acts are identified, particularly focused on competency-based training, following the trend that is currently observed in several countries.