A Hyalinizing Trabecular Tumor (HTT) is a very rare tumor. We report one case that was confirmed to be HTT after an operation. A 44-year-old female visited our hospital with about a 1.3-cm-sized mass on the left thyroid. Fine Needle Aspiration Biopsy (FNAB) indicated papillary thyroid cancer. After a left hemithyroidectomy, a frozen section biopsy reported the possibility of HTT. Therefore, we did not proceed with the surgery. According to the final report, she was diagnosed with HTT. Five lymph nodes were dissected and were found to be benign. Thyroid transcription factor-1 and neuron specific enolase were positive, and in addition calcitonin was negative. Ki-67 was recorded to be less than 5%. She was discharged without any complication. HTT is benign in most cases, but the possibility of malignancy should be considered. Because it is hard to differentiate between it and PTC or MTC, an accurate diagnosis through histologic examination of specimens and surgical resection is necessary.