Left ventricular pseudoaneurysm is a partial cardiac rupture, contained by the surrounding pericardium that maintains communication with the left ventricular lumen. Whereas most cases of left ventricular pseudoaneurysms are related to myocardial infarction (loss of myocardial integrity), only a handful are associated with valve surgery. We present a female patient, who was admitted for elective mitral valve replacement. After the implantation of the mechanical valve, we encountered a rupture of the atrioventricular groove. After 3 months, a left ventricular pseudoaneurysm was found and the patient was reoperated. The valve was explanted and the inspection of the annulus and previously implanted pericardial patch revealed a loosened stitch on the inferior (ventricular) side. The defect was reinforced with additional stitches and the valve was reimplanted. In conclusion, we report an unusual case with two serious complications after mitral valve replacement - atrioventricular groove rupture and left ventricular pseudoaneurysm.