The aim of this study was to investigate the clinical and radiologic efficacy of autologous platelet-rich fibrin (PRF) in the treatment of intrabony defects associated with localized aggressive periodontitis (LAP). A total of 30 sites, 2 sites per individual in 15 LAP patients, were treated with modified flap operation (MFO; Kirkland flap) alone or combined with autologous PRF. The study variables included plaque index, sulcus bleeding index, probing depth (PD), clinical attachment level (CAL), and gingival marginal level at baseline and 12 months postoperatively. The radiographic bone fill (RBF) on standardized radiographs was assessed after a year using image analysis software. The improvements in PD, CAL, and RBF in test sites compared to control sites were statistically significant (P .05). Mean CAL gain and bone fill in the test sites were 4.0 ± 0.63 mm and 3.09 mm, respectively. Almost 80% of the PRF-treated sites showed ≥ 50% bone fill with minimal marginal tissue recession. Use of PRF significantly enhances the clinical and radiographic outcomes of open flap debridement in the treatment of periodontal intraosseous defects in patients affected by LAP.