Authorities said 32 of 40 wards and communes were submerged by 1-1.5 metres of water, rising to 2.5 metres in low-lying zones.
The Huong River surged above alarm level three, with water nearly reaching the underside of Truong Tien Bridge.
Residents used boats to move along flooded streets near the Imperial City, where strong currents swept through the Ngo Mon Gate.
Several national treasures, including the Nine Cannons, were partially submerged.
Many streets, shops and underground car parks were inundated, leaving vehicles stranded.
Locals moved cars and motorbikes onto bridges to avoid flood damage.
Floodwaters also entered Hue Central Hospital, forcing police and soldiers to evacuate patients and medical equipment to higher floors.
Intersection of Dien Bien Phu and Nguyen Hue streets seriously inundated
Landslides and flash floods were reported in mountainous areas, cutting off traffic on several routes.
The central region, including Hue, is forecast to face torrential rain until October 29.
