BACKGROUND The aims of the present study was to compare midterm results of quadrangular leaflet resection versus chordal replacement for the repair of degenerative posterior mitral leaflet (PML) prolapse, and to explore the risk factors for recurrent severe mitral regurgitation (MR). METHODS From January 2012 to December 2018, 1,423 consecutive patients underwent mitral valve (MV) repair. A total of 317 had degenerative PML prolapse and constituted the study population. Of these, 74 (23.3%) underwent quadrangular leaflet resection, and 243 (76.7%) underwent chordal replacement. Outcomes were compared by using unadjusted data and propensity score-matched analyses. RESULTS Patients with multiple leaflet prolapse were more likely to undergo chordal replacement (18.4% vs. 41.9%, P<0.001), and performed as a minimally invasive approach (47.3% vs. 61.7%, P=0.027). Of the entire cohort, 1 death (0.3%) occurred due to intraoperative aortic dissection, and 1 patient who had undergone chordal replacement required reoperation before discharge for posterior leaflet tearing. There was no significant difference in the probability of freedom from recurrent severe MR at 82 months between the resection and neochordae groups in both the pre-matched (95.6% vs. 88.8%, P=0.105) and matched (95.2% vs. 88.5%, P=0.170) cohorts, which was consistent across all of the examined subgroups (P>0.05). Multivariate Cox regression indicated that dilated left ventricular end-systolic diameter (LVESD) was an independent risk factor for recurrent severe MR [<40 vs. >40 mm, hazards ratio (HR): 3.17, 95% confidence interval (CI): 1.20-8.39, P=0.020]; however, surgical technique was not (resection vs. neochordae, HR: 0.31, 95% CI: 0.07-1.37, P=0.122). CONCLUSIONS Chordal replacement for the repair of degenerative posterior MV prolapse yields similar satisfactory outcomes when compared with quadrangular resection, and is promising in minimally invasive cardiac surgery for various lesions. However, it is also associated with more recurrent severe MR, albeit non-significant, for which patients with dilated LVESD are at high risk.