<p>Exercise testing and counseling are essential to optimizing fitness and outcomes of patients with tetralogy of Fallot (TOF). In this population, aerobic fitness is inversely related to disease severity, morbidity and mortality. Right ventricular remodeling, maldistribution of pulmonary blood flow, ventilatory inefficiency, restrictive lung physiology, and electrical abnormalities can negatively impact the exercise capacity of TOF patients. These physiologic abnormalities can be further exacerbated by deconditioning resulting from inadequate physical activity and exercise. Current guidelines recommend cardiopulmonary exercise testing (CPET) to inform management of TOF patients. CPET is important for routine surveillance, evaluation of exertional symptoms, decision making related to intervention, prognostication, and exercise counseling. Understanding exercise-related factors including information from the CPET and exercise history is critical to provide effective exercise promotion, prescription, and/or exercise training to improve fitness of patients with TOF. We present the “TOF CPET Stoplight,” a framework for utilizing CPET findings to inform exercise testing and counseling. Red Zone findings include VO2 max &lt; 65% predicted, accelerated VO2 max decline, and elevated VE/VCO2 slope &gt; 39, which warrant consideration of a supervised, monitored fitness training program and more frequent CPET surveillance. Green Zone findings provide reassurance but these patients should continue periodic surveillance CPET and ongoing exercise counseling and promotion. Through this review, we aim to provide a practical resource for the pediatric and congenital cardiologist to harness the clinical utility of CPET and counsel their TOF patients to engage in regular exercise safely and effectively.</p>