Rosai Dorfman disease (RDD) or sinus histiocytosis is a rare, idiopathic, non neoplastic histiocytic proliferation of unknown etiology typically presenting with massive cervical lymphadenopathy with or without systemic involvement. It may occur in any age group, but is most commonly seen in children and young adults. We report a case of RDD with bilateral massive cervical swelling in a 21 years old pregnant female. The swelling progressively increases in size after the onset of pregnancy. FNAC was advised. The cytomorphology revealed lymphocytes, plasma cells and uni to multinucleated histiocytes with lymphophagocytosis and the diagnosis of RDD was rendered. It is concluded that FNAC is a reliable and useful tool for the diagnosis of sinus histiocytosis with massive lymphadenopathy (RDD) and biopsy can be avoided, thus reducing the inconvenience to the patients especially in pregnancy.