The road was closed on Tuesday afternoon after a major diesel spill from a fuel tanker damaged a quarter of a mile section between Hoyles Road and Swains Lane.
Work on another road in the county was postponed to allow Highways workers to tackle the A38 immediately. They have now resurfaced the damaged road and replaced the road markings.
Cllr Harvey Siggs, Somerset County Council’s Cabinet member for Highways, said: “I’m delighted to hear that we have been able to reopen the A38 so quickly.
“Major diesel spills like this cause significant damage to roads by making the surface slippery and softening the tarmac – meaning a full resurfacing is the only option.
“By redeploying a gang from another job we have been able to make the repairs and reopen the road within 48 hours which is a tremendous effort.
“Thanks to them for their hard work, and thanks to motorists for their patience during this extreme set of circumstances.”
Highways teams worked closely with partners during the incident. Wessex Water suspended work on Mantle Street in Wellington and removed temporary traffic lights to improve traffic flow, while Rights of Way staff helped close off footpaths to keep walkers away from the site.
Cllr Siggs added: “I’d like to thank our partners too for all their support in helping us respond to this incident. A brilliant team effort."