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Langerhans cell histiocytosis (LCH) is a rare illness with an incidence of 0.5–5.4 per million individuals. Isolated thyroid gland involvement is an unusual presentation of LCH that can mimic malignancy and pose a diagnostic challenge for clinicians. We report a case of unifocal LCH involving thyroid gland in a 12 year boy. Fine Needle Aspiration Cytology (FNAC) smears were highly cellular comprising of numerous eosinophils, lymphocytes, macrophages, neutrophils along with large Langerhans cells (LCs) having abundant granular cytoplasm, irregular nuclei and longitudinal nuclear grooves. On immunocytochemistry these cells were S-100 positive. Our case discusses the characteristic cytological features and differential diagnoses of unifocal LCH involving the thyroid gland, emphasizing the diagnostic utility of FNAC in such an unusual clinical presentation, thus obviating the need of biopsy