The US actor will be the show's first non-British host in its 39-year history, reported BBC.
"Matt's a lifelong fellow petrolhead and I'm thrilled he's joining Top Gear," said Chris Evans of his new on-screen colleague.
Additional Top Gear cast members will be confirmed shortly.
"As a car nut and a massive fan of Top Gear, I'm honoured and excited to be a part of this iconic show's new chapter. "What a thrill!," said LeBlanc.
The 48-year-old is best known for his role as Joey Tribbiani in "Friends" and has more recently been seen, as himself, in BBC Two sitcom "Episodes".
Evans was named as Top Gear's new host last year after the BBC opted not to renew Jeremy Clarkson's contract in the wake of his much-publicised "fracas" with a "Top Gear" producer.
Clarkson subsequently signed up with streaming service Amazon Prime to present a new motoring show with Richard Hammond and James May, his former "Top Gear" co-presenters.