BACKGROUND Thyroid incidentalomas are typically nonpalpable thyroid nodules discovered during radiographic evaluation for a non-thyroid issue. Thyroid incidentalomas visualized by computed tomography (CT) and ¹⁸F-flurodeoxyglucose (FDG) positron emission tomography (PET) before living donor liver transplantation (LDLT) are rare. The aim of the study was to analyze the clinical impact of thyroid incidentalomas discovered prior to transplantation. MATERIAL AND METHODS This retrospective study recruited 1010 patients undergoing LDLT between 2010 and 2019. CT was performed on each patient, whereas PET was performed on randomized patients (n=498). RESULTS The prevalence and malignant risk of thyroid incidentaloma on CT was 2.3% (23/1010) and 13.0% (3/23), respectively. The prevalence of thyroid incidentaloma on PET was 3.0% (15/498). Approximately half of the FDG uptake on PET was diffuse uptake (n=7), whereas the other half was focal uptake (n=8). The malignant risk of PET incidentaloma with focal FDG uptake was 37.5% (3/8). Four asymptomatic thyroid cancers were identified incidentally. After total thyroidectomy followed by LDLT, these patients maintained cancer-free status. CONCLUSIONS Thyroid incidentalomas occurred at a rate of 2-3% in LDLT candidates. The malignant risk was 13.0% on CT incidentaloma, and 37.5% on PET incidentaloma with focal FDG uptake. Curative treatment of incidental thyroid cancer followed by LDLT without delay can achieve a favorable prognosis.