© 2021 John Wiley & Sons LtdBackground: It is known that serum thyroglobulin (TG) can increase after fine-needle biopsy of thyroid nodules. We aimed to determine whether TG is increased after ultrasonography (US)-guided fine needle capillary biopsy (FNC) of suspicious cervical lymph nodes (LNs) in thyroidectomised patients and investigate the possible association between change in TG and cytology results. Material and Methods: Data of 188 patients who underwent FNC of suspicious cervical LNs were retrospectively evaluated. Demographical, laboratory and ultrasonography features of LNs were noted. TG levels before FNC (TGb-FNC), after FNC (TGa-FNC), TGa-FNC/TGb-FNC ratio and the number of patients with increased TG were determined. Patients were grouped as benign, nondiagnostic, suspicious for malignancy and malignant according to the cytological results. Results: TGa-FNC, TGb-FNC/TGa-FNC and rate of patients with increased TG were significantly higher in malignant cytology group than other groups (P <.001). The optimal cut-off level of TG increase that was predictive for malignancy was 7.6% with a sensitivity of 73.7% and specificity of 85.2%. TG increase was not associated with age, sex, Thyroid-stimulating hormone (TSH) level, anti-TG positivity and US features of LNs while significantly lower in patients who received radioactive iodine (RAI) treatment. Among 31 patients with positive anti-TG, TGb-FNC/TGa-FNC, and rate of patients with increased TG were higher in malignant compared to benign and nondiagnostic cytology groups. Conclusions: Serum TG increment and rate of patients with increased TG after FNC of suspicious cervical LNs were higher in patients with malignant cytology than with all other cytology results both in all study group and in sub-group of anti-TG positive patients. Increase in TG after FNC might be an additional tool for determining LN metastasis.