The Korean Society of Radiology and the National Evidence-based Healthcare Collaborating Agency developed the guideline for primary imaging and biopsy methods in the diagnosis of thyroid nodules. The development committee, the working committee, and the advisory committee were formed to develop the recommendation. The development committee mainly plays a role of methodological consulting and overall planning and management of the advisory development stage. The working committee was composed of experts recommended by the Korean Society of Thyroid Radiology and conducted a practical adaptation process from the selection of core questions to the final recommendation. The Advisory Committee consisted of clinical experts recommended by the Korean Thyroid Association and reviewed core questions and draft recommendations and participated in the Expert Panel Survey. This guideline recommends cervical ultrasound as the first imaging modality for diagnosis of suspected thyroid nodules and recommends ultrasound-guided fine needle aspiration for histologic diagnosis of thyroid nodules. This guideline is expected to be of significant benefit to clinicians treating thyroid nodules.