OBJECTIVE: To evaluate the reason for delay of surgical referral in tertiary hyperparathyroidism (THPT) and its impact on renal allograft function. BACKGROUND: Persistent hyperparathyroidism after renal transplant has been shown to negatively impact allograft function, yet referral for definitive treatment of THPT is often delayed. METHODS: A retrospective review was performed of patients undergoing parathyroidectomy for THPT (n = 38) at a single institution from May 2016 to June 2018. The first elevated serum calcium after transplant and time to referral for parathyroid surgery were recorded. Baseline creatinine post-transplant and the most recent creatinine level were used to assess allograft function. RESULTS: Thirty-eight patients were included, with mean age 53 ± 2 years and 66% male. Mean preoperative calcium and parathyroid hormone were 10.8 ± 0.1 mg/dL and 328 ± 48 pg/mL, respectively. THPT after renal transplant was diagnosed at a median of 15 days (range of 1-4892 days). Median time to parathyroidectomy referral was 320 days (range 16-6281 days). In over 50% of patients, the cited reason for referral to an endocrine surgeon was difficulty with cinacalcet - either cost, poor calcium control, and poor compliance or tolerance. In comparing renal function between patients referred early (<278 days, n = 19) versus later (>278 days, n = 19) for parathyroidectomy, those referred early had an improvement in creatinine (27.6% vs -5%, P = 0.007). CONCLUSIONS: Patients with THPT wait approximately a year, on average, before referral to an endocrine surgeon for curative parathyroidectomy; earlier referral was associated with improvement in serum creatinine.