Physical activity prescription is one of the most important services we can provide to our patients who are sedentary or who have a chronic condition, but many of us have not been given adequate training on how to do it. This Masterclass aims to bridge that gap. The class teaches the basics of physical activity prescription using a variety of approaches. It explores the different types of activities, exercise intensities, safety precautions, disease-based modifications, and barriers and facilitators for patients and providers. After reviewing the basics, a case study on a patient with a chronic condition is presented to demonstrate how we prescribe physical activity in ‘real life’.