We present a case of splenic rupture as the cause of a sudden drop in blood pressure soon after mitral valve surgery for infective endocarditis. This case suggests that, in addition to more common causes of unstable vital signs after valvular surgery, such as cardiac tamponade or bleeding at the operation site, splenic rupture, although rare, should be considered in the differential diagnosis. This is particularly important in the case of infective endocarditis.