At 03:55, East Sussex Fire & Rescue were called to a fire in a ground floor shop and domestic flat above on Warren Road, Woodingdean, Brighton.
As at 05:45 crews had surrounded the fire and steady progress has been made to put the fire out.
At the height of the incident six Breathing Apparatus, four Hose Reel jets, 1 in 7 foam and the Aerial Ladder Platform was used to bring the fire under control.
The incident is now being scaled down.
A fire investigation will take place to establish the cause.