Busch said two weeks ago the extension to drive the No. 18 Toyota was nearly completed and he was not a free agent. JGR announced the extension Thursday morning on Twitter.
Terms of driver contracts are never released but most top-tier drivers sign three-year deals. Busch's deal that expired at the end of this season was for three seasons.
His extension parallels longtime sponsor Mars' new deal to remain the primary backer of Busch's car.
Busch and Mars, under M&M's umbrella, joined JGR in 2008. Busch has won 174 national series races in the 10 years since, and he's NASCAR's 2015 Cup champion.
Busch made his 500th career Cup start last week at Atlanta, where he also won the Truck Series race to becomes the winningest driver in that series' history with 52 wins.