We describe a case of a healthy male full-term neonate, 21 days old, admitted to the emergency room, presenting a severe cardiovascular collapse with an initial sinus rhythm. The first diagnostic hypothesis was of septic shock, having antibiotics, fluid resuscitation, inotropic drugs and ventilatory support started immediately. After achieving haemodynamic stability, a new cardiovascular collapse occurred with supraventricular tachycardia (SVT). The latter was successfully treated and the neonate did not suffer any organ damage. Cardiogenic shock should be considered despite being a much rarer cause of shock in neonates. SVT is promptly diagnosed when a cardiorespiratory monitor is available; however, the intermittent occurrence of the tachycardia episodes makes this diagnosis more difficult to recognise and manage.