Firefighters were called to a blaze at a three-storey residential property in Hurst Green, the fire service said.
East Sussex Fire and Rescue Service (ESFRS) said crews were called to a property in Station Road at 4.18pm.
Crews from Heathfield, Hastings, Battle and Bexhill, together with Kent Fire and Rescue were called to attend the scene.
ESFRS asked people to avoid the area.
A spokesman for ESFRS said firefighters used six breathing apparatus and three hose reel jets to extinguish the fire on the ground floor of a three-storey building.
Firefighters are still on scene cutting away and dampening down, ESFRS added.
One person was handed over in to the care of paramedics after suffering smoke inhilation, ESFRS confirmed.
A video from the scene, shared on Twitter, showed firefighters tackling flames coming from the front of a residential property.
The A265 was closed and there was very slow traffic due to the fire, according to reports.
Traffic reports said vehicles were not able to pass between A21 London Road and Great Oak.