The Hoan Kiem District resident was pronounced dead by doctors at Bach Mai Hospital on Wednesday.
They said the patient had a fever for five days but bought medicines himself to treat it, and by the time he was hospitalized the disease had caused liver and kidney failure.
He was given dialysis and intensive care, but to no avail.
He died of septic shock and blood clotting disorder.
Hoan Kiem health authorities have disinfected the man’s neighborhood.
Two weeks ago a 17-year-old had died of dengue in Nam Tu Liem District.
The teenager was reportedly worried about contracting Covid-19, and so his family did not take him to hospital.
He was taken to Bach Mai for emergency treatment after he suffered from hypoperfusion shock when given intravenous fluids at home.
Experts from Hanoi’s Center for Disease Control and Prevention said now is the peak dengue fever season, which usually runs from April to October in the north and June to December in the south, and called on the public to be cautious against the mosquito that spreads the disease.
Vietnam had recorded 36,253 dengue cases in the year to mid-July, including three deaths in the south central province of Binh Dinh and the southern provinces of Binh Phuoc and Tay Ninh, according the Health Ministry.
The number of deaths dropped by 10 cases and the number of infections dropped by 58.6 percent from the same period last year.