Dengue fever/dengue haemorrhagic fever (DF/DHF) appears to be emerging in Hanoi in recent years. A case-control study was performed to investigate risk factors for the development of DF/DHF in Hanoi. A total of 73 patients with DF/DHF and 73 control patients were included in the study. The risk factor analysis indicated that living in rented housing, living near uncovered sewers, and living in a house discharging sewage directly into to ponds were all significantly associated with DF/DHF. People living in rented houses were 22 times more at risk of DF/DHF than those living in their own homes [adjusted odds ratio (aOR) 22, 95% confidence interval (CI) 11-46]. People living in an unhygienic house, or in a house discharging sewage directly to the ponds were 34 times and 43 times, respectively, more likely to be associated with DF/DHF (aOR 34, 95% CI 1-117; aOR 43, 95% CI 11-169). These results contribute to the understanding of the dynamics of dengue transmission in Hanoi, which is needed to implement dengue prevention and control programmes effectively and efficiently.