: This study evaluated the outcomes of single open-flap debridement, open-flap debridement (OFD) plus resorbable membrane placement, and OFD with resorbable membrane placement plus platelet-rich fibrin (PRF) in terms of periodontal clinical parameters and glycated hemoglobin (HbA1c) levels in 24 adult patients with stage 3 grade C periodontitis and type II diabetes mellitus. : The primary outcome measure for this study was the clinical attachment level (CAL); secondary outcomes included additional periodontal parameters, such as the plaque index (PI), bleeding on probing (BOP), probing depth (PD), as well as glycated hemoglobin (HbA1c) levels to evaluate the systemic impact of the treatments on glycemic control. The parameters were assessed before and at three and six months post-surgery. In Group A, the flap was sutured closed; in Group B, an absorbable collagen membrane was placed over the defect; and in Group C, PRF was utilized in the defect, with two additional PRF membranes used to cover the defect. The wound healing index (WHI) was recorded at 7 and 14 days after the surgery. : The initial findings indicated no significant differences in the periodontal parameters among the three groups. However, improvements in the PD and CAL were most notable in Group C, followed by Group B, with Group A showing the slightest improvement. At six months, there was a highly significant difference in the CAL ( < 0.001). Group C (4.92 ± 0.35) and Group B (4.99 ± 0.31) demonstrated the most significant improvements in the CAL compared to Group A (5.89 ± 0.57). At seven days post-surgery, Group C demonstrated significant healing, with 85% of the sites showing complete healing. By the 14-day mark, all sites in Group C indicated complete healing. Although the HbA1c values did not exhibit statistically significant differences among the groups at baseline, at the 6-month evaluation, all groups showed significantly lower values than baseline. However, the comparison between groups revealed significantly improved values for Group C. : The study's results suggest that PRF is an exceptional material for infrabony defects treatment and notably improves HbA1c levels.