Grade III furcation involvement presents a significant periodontal challenge due to complete interradicular bone loss and limited regenerative potential. This case report described the management of a Grade III furcation defect using guided bone regeneration (GBR) and evaluated over a 9-month follow-up period. Following meticulous debridement, the defect was treated with a bone graft and barrier membrane to facilitate selective cell repopulation. Progressive improvement in probing depth, clinical attachment level, and radiographic bone fill was observed. The findings suggested that GBR may offer a predictable regenerative approach for selected Grade III furcation defects when proper case selection and surgical protocols were employed.