Objective: To assess the meaning of a physical activity prescription (PAP) from the physician’s point of view and to examine current PAP-related clinical practices and stage of change, including the factors that influence them. Methods: Mixed methodology was applied to obtain valid, high-quality data. During the qualitative phase, the “free-listing” technique was used to explore the “cultural domain” of a physician’s perception of PAP, as well as the construction of culturally relevant items used during the last phase of the study. A survey was conducted to evaluate clinical practices, attitudes, and physician state of change regarding PAP. The convenience sample of 58 (qualitative phase) and 350 internists (quantitative phase) who attended the International Congress of Internal Medicine was interviewed. Results: A majority of internist reported having adequate knowledge, positive attitude, being in the maintenance phase with no barriers to prescribe physical activity (PA). Prescription was associated with physician training, their workplace, and experience. However, physicians do not satisfactorily evaluate the level of patient’s PA nor recommend an adequate level of PA, which is necessary to achieve health goals. Conclusions: Physicians had great acceptance of PAP. However, there were low levels of knowledge of current PA guidelines, although most physicians thought they had sufficient knowledge. Training seems to be an excellent way to improve PAP.