Giant cell granulomas (GCG) are uncommon benign tumor-like lesions mostly arising in the oro-facial area. They are more common in women and occur in patients younger than 30 years. Lesions restricted to the bone are referred to as central giant cell granulomas (CGCG), and those developing primarily on soft tissues are termed peripheral giant cell granulomas (PGCG). Both types are histologically identical. The combination of both clinical examination and radiography allows for the differentiation of those two variants. On rare occasions GCG, and especially CGCG, may develop in relation to hypercalcemia linked to hyperparathyroidism (HPT). In those cases, the GCG treatment prognosis is closely linked to the HPT management. Therefore, patients diagnosed with a GCG must be investigated to search for an HPT. Reported herein is a rare clinical case of a mandibular PGCG which led to the diagnosis of primary HPT.