This randomized study compares patient pain and comfort during ultrasound-guided thyroid fine needle biopsy using 21-gauge versus 27-gauge needles. Patients with thyroid nodules were randomly assigned to one of two needle sizes. Pain intensity was measured immediately after the procedure using a 0-100 Visual Analog Scale. The study was conducted at İzmir Atatürk Training and Research Hospital between January 2024 and March 2024. The aim is to determine which needle size causes less pain and better patient comfort during the biopsy procedure.