A former assistant for the 88-year-old Dinkins told NBC 4 New York he was at New York Presbyterian Hospital "with a touch of penumonia and getting some much needed rest."
"He will be in through the weekend, but is expected to be all right," said Dinkins' former assistant.
Dinkins was treated for pneumonia at the same hospital in 2013.
Dinkins, the city's first black mayor, served one four-year term that began in 1990. The prominent Municipal Building at the base of the Brooklyn Bridge was renamed for him last fall.