The false aneurysm of the left ventricle is a rare complication after a mitral valvular surgery. It results from the rupture of the ventricular wall inside an adhering pericardium, thus constituting a cavity whose wall is devoid of myocardial elements and communicates with the ventricle by a large collar. Its clinical presentation remains not very specific with an insidious spontaneous evolution which is generally done towards rupture with sudden death by tamponade. Various sophisticated modern diagnostic techniques allows a precise diagnosis. The letal nature of this lesion must be recognized and justifies an immediate surgical repair. We report the case of a 68 years old patient who presented herself in consultation of cardiology with a NYHA IIb (New York Heart Association) cardiac failure 4 months after a surgery of mitral valvular replacement. The transthoracic echography showed a voluminous false aneurysm of the left ventricle confirmed by cardiac CT scan. She has benefited from an anevrismectomy with good clinic evolution. This observation illustrates the late and silent character of the development of the false aneurysm of the left ventricle after mitral valvular surgery.