Demographic data and blood samples (5 mL / patient) were collected from 765 patients suspected of having DF / DHF from all medical and paediatric wards of the Teaching Hospital, Jaffna from 2009 to 2012. Viral RNA was extracted from patients’ sera using Qiagen viral RNA mini kit (Cat No 5206). Identification and typing of DENV were carried out using a combination of RT-PCR and a single-tube multiplex PCR. Primers described by Lanciotti et al were used to detect the C and PrM genes of the DENV.All 4 serotypes of dengue viruses (DENVs) have been co-circulating in Sri Lanka for more than 3 decades. However, people in the Northern part of Sri Lanka were isolated from the rest of the country due to travel restriction as a result of recently ended war. Thus the circulating DENV in the Northern part of Sri Lanka has not been investigated and this is such a study to describe the epidemiology of DENV serotypes and their association to DHF in the northern Sri Lanka from 2009 to 2012.