Symptoms of heart failure (HF) should be alleviated as quickly as feasible. Apart from standard pharmacological therapy, supplementation of oxygen is lifesaving in hypoxemic (SpO2 <90% or PaO2 <60 mmHg) HF patients. For sick patients with SpO2 <85%, respiratory distress (respiratory rate >25 breaths per min) and pulmonary edema, along with oxygen administration, noninvasive positive pressure ventilation (NIPPV) methods, including BiPAP/CPAP or humidified high-flow nasal oxygen, should be tried to optimize oxygenation, reduce work of breathing and to reduce the venous return. If these noninvasive ventilatory support methods fail to improve hypoxemia, endotracheal intubation and mechanical ventilation should be instituted. Short-term mechanical circulatory support (extracorporeal membrane oxygenation) devices are reserved for cardiogenic shock patients due to advanced HF associated with reversible end-organ failure and hypoxia. These temporary mechanical circulatory support devices are also useful as a bridge to long-term mechanical circulatory support or heart transplant in end-stage HF with refractory cardiogenic shock. Even though the use of additional oxygen is a standard practice for hypoxemic patients, routine use of high concentrations of oxygen via inhalational therapy or NIPPV for normoxemic HF patients may result in hyperoxemia. Hyperoxemia has been shown to have negative hemodynamic effects like increased systemic vascular resistance, reduced cardiac index, and decreased coronary blood flow. Detailed prescription by the treating physician, careful monitoring, and meticulous titration of oxygen is essential for safe oxygen treatment for HF patients.