Introduction: For deep intrabony defects or Class II furcation involvements (FI), periodontal tissue regenerative therapy combined with bone graft materials and a barrier membrane is recommended. The objective of this study was to assess the safety and efficacy of using carbonate apatite (CO(3)Ap) granules and absorbable poly(lactic acid/caprolactone) (PLCL) membranes for periodontal regeneration in the treatment of intrabony defects and mandibular Class II FI. Methods: This prospective pilot clinical study, conducted at a single center with a single-arm design, aimed to assess the safety and efficacy of CO(3)Ap and PLCL membranes in patients with periodontitis. A total of 9 patients with 10 teeth, including seven deep intrabony defects and three Class II FI, were treated with CO(3)Ap granules and PLCL membranes. Clinical parameters such as probing pocket depth (PPD), clinical attachment level (CAL), bleeding on probing (BOP), tooth mobility (Mo), Plaque Index (PI), and Gingival Index (GI) were assessed at baseline, 6 and 12 months post-surgery. Radiographic analysis was performed using dental X-rays and cone beam computed tomography (CBCT) images taken at baseline, 6, and 12 months post-surgery. Results: Postoperative healing was uneventful in most of the cases. In some cases, membrane exposures were observed. However, there were no signs of inflammation, such as abnormal bleeding, pain, swelling, or pus. These exposures eventually healed well in the end. The mean reductions in PPD at 6 and 12 months were 4.5 +/- 1.6 mm and 4.9 +/- 1.4 mm, respectively, while the mean gains in CAL were 4.4 +/- 1.7 mm at 6 months and 4.6 +/- 1.2 mm at 12 months. Radiographic analysis showed improvements in linear bone height within intrabony defects and in the vertical subclassification of FI in Class II FI. Conclusions: Despite the limitations of this study, periodontal regenerative therapy using CO(3)Ap granules and a PLCL membrane demonstrated promising clinical safety and efficacy for treating intrabony defects and mandibular Class II furcation involvement.