Thyroid incidentalomas on fluorine-18-fluorodeoxyglucose positron emission tomography–computed tomography (18F-FDG-PET-CT): A tertiary care hospital experience in South India. Aim: To find the prevalence and clinical significance of unexpected focal uptake of 18F-FDG or nodules in the thyroid gland of consecutive PET-CT studies. To find the maximum standardized uptake value (SUVmax) of benign and malignant thyroid incidentalomas in FDG-avid lesions. Materials and methods: A total of 2,699 18F-FDG-PET-CT studies from January to December 2018 were reviewed. Studies with incidental focal 18F-FDG uptake with SUVmax, sonography, cytology, and histopathological results were compiled and analyzed. FDG nonavid thyroid nodules on CT were also studied. Results: In 312/2,699 patients with thyroid nodules, 18F-FDG uptake was identified in 139 (5%)—focal (76) and diffuse (63). In the cases with focal uptake, 42 were further evaluated, of which ultrasound (USG) showed thyroid imaging reporting and data system (TIRADS) 2/3 in 21 cases, TIRADS 4/5 in 20 cases, and 1 patient underwent surgery. Final histopathological examination (HPE) was suggestive of papillary thyroid carcinoma. The mean SUVmax in malignant nodules (20.20) was significantly higher (p < 0.03) than benign nodules (6.12), but there was considerable overlap (benign: 3.75–10.25; malignant: 3.34–48.32) between them. Among FDG nonavid nodules (173), only 24 were followed up with sonography [7/24 (29.16%) had TIRADS 4/5 lesions]. Only 2/173 were diagnosed with malignancy. Conclusion: Thyroid incidentalomas, though infrequent, showing 18F-FDG uptake should be evaluated with sonography followed by biopsy/fine needle aspiration (FNA) if required, to rule out malignancy. The SUVmax value was significantly lower in benign incidentalomas compared to malignant nodules; however, there was no clinically useful SUVmax cutoff value to determine malignancy due to considerable overlap between them. Clinical significance: Thyroid carcinomas detected by 18F-FDG-PET-CT are more aggressive than those detected by other imaging modalities. From our study, we found that there is a prevalence of at least 5% of thyroid incidentalomas. Therefore, understanding the importance of further steps in evaluation is needed to avoid unnecessary investigations and also to avoid missing the possibility of detecting malignancy. This study also stated that having a cutoff value for SUVmax is ambiguous in differentiating between benign and malignant nodules.