Case Description: An eight-year-old, castrated male keeshond presented with a history of testing positive for the primary hyperparathyroidism (PHPT) gene, ionized hypercalcemia, parathyroid hormone (PTH) level within the reference range, polyuria, polydipsia, and an episode of tremors. Clinical Findings: Physical examination was largely unremarkable. Biochemical testing confirmed total and ionized hypercalcemia, and PTH concentration within the reference range. Ultrasound examination detected a hypoechoic mass cranial to the right thyroid gland. Treatment and Outcome: The enlarged parathyroid gland was surgically removed. Histopathology confirmed complete excision of a solitary parathyroid adenoma. The patient was monitored postoperatively for seven days. Mild ionized hypocalcemia developed two days postoperatively, and resolved five days postoperatively. Seven weeks later, the dog had maintained ionized normocalcemia. Clinical Relevance: This case provides a framework for discussion of clinical aspects of PHPT, including clinical signs, diagnostic approach, treatment options, and prognosis. Discussion also includes pathophysiology and genetic aspects of PHPT in keeshonden.