The cell origin, histopathologic features, and prognosis of medullary and papillary thyroid carcinoma are different and to have them occur simultaneously in a single patient is a rare occurrence. This is a case of a 38-year-old female who presented with an enlarging anterior neck mass whose fine needle aspiration biopsy could not rule out a papillary lesion. Thus, she was advised to undergo total thyroidectomy, and her final histopath showed a simultaneous medullary and papillary thyroid carcinoma. Her initial serum calcitonin was elevated at 252 pg/ml, and it remained persistently elevated over the course of 7 months. A repeat ultrasound revealed solid nodules with coarse calcifications and enlarged lymph nodes at both submandibular regions. This warranted a repeat surgery with neck dissection with the finding of eight lymph nodes positive for metastatic carcinoma. On follow up after her second surgery, the calcitonin decreased to 42.70 pg/ml. Knowledge of this simultaneous occurrence of medullary thyroid carcinoma and papillary cancer is important for its prognostic implications and therapeutic plan.