Cameron Smith has fallen just short of victory in his maiden LIV Golf tournament but still banked over $A1 million for his efforts in Boston.

Australia's world No.2, who became the highest-profile golfer to join Greg Norman's Saudi-funded league last week, shared the lead with two holes to play but sent his tee shot into the bushes, with his first bogey of the round a costly one.

It meant Smith dropped out of contention for the three-way sudden-death play-off, which was won by Dustin Johnson who nailed a 35 foot eagle putt to seal the win.

The victory was the American's first in 19 months, finishing ahead of two other LIV Golf debutants in Chile's Joaquin Niemann and Indian Anirban Lahiri.

Smith's final round of seven-under 63 saw him finish in a tie for fourth at 14 under alongside Englishman Lee Westwood, who carded a 62.

The Queenslander started with a bang in the opening round, posting a six-under 64 that included a 45-foot eagle putt.

But the British Open champion dropped down the leaderboard on day two when he signed for a one-under 69 to share eighth spot.

"I thought I was really out of it after the second round as I played pretty poorly but to get out here today and to do what I did was pretty cool," Smith said.

"It was just an unfortunate bogey there on the second last hole and it cost me a spot in the play-off."

Upon signing deal worth a reported $A140 million to join the rebel tour Smith said he was excited about the music and vibe at LIV tournaments and wasn't disappointed by his first outing.

"It was great out there - the competition is fantastic," he said.

"It's loud and it feels like the course has a heartbeat. I love that and can't wait to keep going."

Johnson, who closed with a five-under 65, needed a birdie on the par-5 18th to take the outright win but with his drive going into the rough had to settle for a par and join Lahiri (64) and Niemann (66) at 15-under 265.

But luck went his way in the play-off when his fast-moving putt hit the back of the cup and dropped in, securing a pay cheque of $A5.9 million.

"It was going a little fast, but it was a good line," Johnson said with a big smile.

"I got some unlucky breaks (on No. 18) the first time around. It owed me one and I got it."

Smith was joined by Marc Leishman in an All-Australian team with Wade Ormsby and Matt Jones also on board.

Called Punch GC the team finished in a tie for sixth with Johnson's outfit taking the spoils.

On the individual leaderboard Leishman (72) and Jones (70) both finished tied for 26th at four under, as did reigning Australian PGA champion Jed Morgan who carded a final round 65.

Ormsby (70) was 43rd in the 48-man field.

The next LIV Golf Invitational series is in two weeks in the Chicago suburbs at Rich Harvest Farms, best known for hosting the Solheim Cup in 2009.