The invasive cardiopulmonary exercise test (iCPET) provides a comprehensive, simultaneous evaluation of an individual’s cardiovascular, respiratory, and metabolic response to exercise. The test is uniquely suited for the evaluation of exercise intolerance, as well as the deep phenotyping of disease states including pulmonary arterial hypertension and post–coronavirus disease symptomatology. Despite an expanding list of clinical and research applications, both the complexity of the test and a lack of familiarity with how the test is performed have been barriers to the widespread use of iCPET. The aim of this article is to provide practical insights into how an iCPET is performed.