Dengue fever (DF) is an emerging mosquito borne viral disease and important public health problem in low land of Terai region which is also expanding to hilly region. This study was designed to estimate sero-prevalence of dengue virus infection in the post monsoon period (Jun-Dec) of 2010 in Nepalese patients with fever visiting hospitals of Birganj, Damouli, Biratnagar and Dhading Besi. Serum samples were collected from 280 patients visiting hospitals with history of fever & clinically suspected DF. The sero-prevalence of dengue virus specific IgM was determined by enzyme linked immunosorbent assay (ELISA) kit (SD, Korea). Molecular diagnosis based on RT-PCR was also performed for the confirmatory diagnosis. The IgM capture ELISA has become the most accepted technique for the diagnosis of dengue in developing countries like Nepal.