Primary hyperparathyroidism (PHPT) is present in up to 0.1% of the general population. The incidence is higher in women and increases with age. The majority of the cases is asymptomatic and up to 85% are due to single gland adenoma. Parathyroidectomy is the treatment of choice after localization of the hyperactive gland. Papillary Thyroid Carcinoma (PTC) is the most common cancer of the thyroid and constitutes more than 70% of thyroid malignancies. PTC can present as a single nodule or can be Multifocal. The incidence is higher in women. Early treatment favors a good prognosis. PTC with PHPT has been reported in 2.3-4.3% of patients undergoing surgery for PHPT. The coexistence of parathyroid adenoma and incidental PTC is thought to be rare. The mechanisms underlying the relationship between PHPT and PTC have not been established. We suggest a possible hypothesis for the relationship based on shared embryological origin and genes, high parathyroid hormone (PTH), low 1,25 hydroxy vitamin D, hypercalcemia resulting in high levels of angiogenic growth factors. This promotes the formation of parathyroid adenomas and papillary thyroid carcinoma. Presence of these two diseases can complicate patient management due to untreated hypercalcemia, unrecognized thyroid cancer and need for second surgery if not screened for both diseases carefully.