The authors report two cases of complicated dengue viral infection with acute myocarditis involving young male adults, of which one was fatal. The first case presented with typical signs of myocardial disease: chest pain and diaphoresis with myocardial depression in the electrocardiograph. The second case deteriorated rapidly and demised within the first day of admission. Histology of the heart muscles showed multiple small foci of myocyte necrosis surrounded by lymphocytes, in keeping with viral myocarditis. Both cases fulfilled the World Health Organization (WHO) diagnosis of probable dengue: the first case had positive dengue serology, both IgM and IgG at day six of illness, and the second case was polymerase chain reaction (PCR) positive for dengue and identified as serotype 2. Despite the severe outcome, both cases did not completely fulfil the criteria for dengue haemorrhagic fever (DHF). Although severe cardiac impairment is not commonly reported in dengue infection, it can be life threatening.