A 10-year-old castrated Miniature Dachshund with hypercalcemia showed normal serum levels of parathyroid hormone (PTH-intact) and parathyroid hormone-related protein (PTHrP). Computed tomography revealed no mass formations in the cervical area. However, serum concentration of 1α,25-dihydroxyvitamin D (1,25(OH)2D) was increased and a small nodule in the right thyroid gland was detected by using ultrasound. Therefore, the right total thyroidectomy was carried out. The resected mass was histopathologically diagnosed as a parathyroid adenoma. The patient showed no complications and clinical signs after surgery, and the serum calcium level decreased to the normal range. This case report suggests that the measurement of serum 1,25(OH)2D can be useful for finding out canine parathyroid adenoma patients with hypercalcemia, even when their serum PTH-intact and PTHrP levels are within the normal range.