The Worksop golfer split with Foster in November last year, as the Yorkshireman struggled to overcome a knee injury he suffered before a charity football match.
But Westwood’s agent Chubby Chandler told the Daily Telegraph the duo were reuniting, and they’ll start working together again at Tiger Woods’ World Challenge in California next week.
Chandler said: “Everyone knows that Lee and Billy were a great partnership and it made sense that now Billy is fully fit again that the partnership reforms.”
“They laugh at the same jokes, are both very quick-witted, and Billy knows when something needs saying to Lee. And, of course, he’s a great caddie.”
“So they’ve had their heart-to-heart, sorted out whatever needed sorting out, and Billy will be back on Lee’s bag permanently, starting at Tiger’s event next week.”
Westwood, with Zimbabwean Mike Kerr on his bag, has endured a frustrating year without a victory.
Foster has caddied for Thomas Bjorn and Branden Grace this year, and can list Seve Ballesteros, Sergio Garcia, Darren Clarke and Tiger Woods on his CV.