Endocardial late fractionated potentials during sinus rhythm mapping may reflect abnormal "subendocardial" substrates associated with right ventricular outflow tract (RVOT) ventricular arrhythmias (VAs). The aim of this study was to explore the clinical outcomes of catheter ablation guided by these late fractionated potentials for RVOT VAs in patients without structural heart disease. From January 2016 to March 2018, 28 patients underwent catheter ablation for RVOT premature ventricular contractions (PVCs) or ventricular tachycardia (VT), guided by the EnSite NavX or Velocity V5.0 three-dimensional mapping system (Abbott, St. Paul, MN, USA). Among them, 10 patients (35.7%) were found to have endocardial late fractionated potentials during sinus rhythm mapping (Group 1). Group 2 was composed of 18 patients in whom no endocardial late fractionated potentials were seen. The burden of VAs, acute procedural success, and 3-month clinical outcomes were analyzed. The average duration of late fractionated potentials after the end of QRS during sinus rhythm mapping in group 1 was 45.00 ± 17.15 ms. Baseline demographics and morphology and burden of PVCs were similarly distributed between both groups. Group 1 had higher acute procedural success compared to group 2 (100% vs 66.7%; P = .039). Moreover, at 3-month follow-up, group 1 had lower total PVCs (49 (1-5986) versus 4316 (1-23231); P = .048), PVC burden (0% (0-5.9) vs 4.3% (0-18.9); P = .055), and higher clinical success (100% vs 55.6%; P = .025) compared to group 2. The identification and elimination of endocardial late fractionated potentials during sinus rhythm mapping could improve the acute success and short-term outcomes of ablation for RVOT VAs.