Fire crews were called at 17.52 today (26 October 2021) to the Eastbound carriageway by Coldean Lane/Hollingbury.
The Westbound A27 has been re-opened as of 21.30. The rest remain closed.
The HGV was carrying beer and crews are working with the Environment Agency to contain spillage of the beer and of diesel.
There are no reports of injuries.
Sussex Police are also on scene.
The recovery process is likely to take considerable time and motorists are being urged to continue to find alternative routes.