A 2-month-old female Holstein calf and a 5-month-old female Japanese black calf presented with gingival vascular hamartoma located in the interdental space between the second and third mandibular incisors in the right and left mandibles, respectively. On radiographic or computed tomographic images, osteolytic changes appeared within the mandibular bones adjacent to the masses. The masses were removed along with affected mandibular bone by using unilateral rostral mandibulectomy. After surgery, both cases exhibited a normal appetite and grew normally, with no cosmetic changes or recurrences. Unilateral rostral mandibulectomy can be applied for invasive gingival vascular hamartomas associated with osteolytic changes.