This illustrated review discusses the haemostatic changes seen in patients with severe coronavirus disease 2019 (COVID‐19) infection and their possible causes. We discuss the crosstalk between inflammation and coagulation resulting in high levels of acute‐phase proteins, very high levels of D‐dimers, and absence of disseminated intravascular coagulation seen in patients with severe COVID‐19. There appear to be high rates of venous thromboembolism and also, what has been poorly described before in acute lung injury, a high rate of pulmonary immunothrombosis (thrombosis secondary to inflammation).