Mitral regurgitation (MR) following endomyocardial biopsy is a rare and severe complication. A 70-year-old man with severe MR due to chordal injury caused by left ventricular endomyocardial biopsy is described. In this patient, a few chordae tendineae of the posterior-median papillary muscle were injured by the biopsy forceps. Due to the chordal rupture, both anterior and posterior leaflets were prolapsed and severe MR developed. MR was successfully treated by artificial chordal replacement using extended polytetrafluoroethylene sutures and ring annuloplasty. This mitral valve repair with artificial chordal replacement was considered suitable to treat MR resulting from iatrogenic chordal injury as the leaflets were not involved in the degenerative process and papillary muscle function was preserved. To avoid MR, the transvenous approach should be used routinely for endomyocardial biopsies; biopsy from the left ventricle is not justified.