Background and objective: Platelet-rich fibrin (PRF) is considered as a second-generation platelet concentrate. PRF is a leukocyte and platelet preparation that concentrates various polypeptide growth factors and therefore has the potential to be used as regenerative treatment for periodontal defects. Beta-tricalcium phosphate (β-TCP) is a synthetic alloplastic material, has been used for bone regeneration in a variety of surgical procedures. The purpose of this study was to compare the healing events by modified widman flap procedure MWF with PRF alone or MWF with PRF + ß-TCP in the treatment of intrabony defects in the same patients. Material and Methods: Using a split-mouth design, Ten patients (20 sites) participated in the study (both males and females) suffering from chronic periodontitis with an age ranging from thirty five to fifty five years. In both contralateral defects modified Widman flap (MWF) were performed for each patient, one intrabony defect received PRF only, while the contralateral defect received β-TCP covered by PRF membrane. Clinical parameters such as plaque index (PI),gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL) were recorded at baseline, 3months, and 6 months post-operative. standardized radiographs was taken at the baseline and 6 months post-operative. Result: the result of these study revealed that both treatment modalities led to highly significant improvement in the mean PD and CAL compared with the baseline. In two treatment modalities there was no statistically significant changes in both (GI )and (PI)scores throughout the study . And after 3 months there was no statistically significant changes in PPD and CAL. While After 6 months measurements revealed a significantly greater reduction in pocket depth in the PRF+ TCP group (3.7 ± 0.7 mm) when compared with the PRF group (4.6 ± 0.5 mm). The PRF group presented with significantly higher mean clinical attachment loss (4.3 ± 0.8) than PRF + ß-TCP PRF( 2.12 ± 0.68) .The mean and standard deviation values of CAL were 4.3 ± 0.8 mm with PRF is 3.5 ± 0.8 mm with PRF + ß-TCP. There was a statistically significant difference between the two groups (P- value = 0.046). PRF group showed the significantly higher mean clinical attachment loss than PRF + ß-TCP. Conclusion: The results of this study indicate that PRF can improve clinical parameters associated with human intrabony periodontal defects, β-TCP and has the ability to augment the effects of PRF in reducing pocket depth, improving clinical attachment levels and promoting defect fill.