Johnson will headline the new competition's inaugural event, which is set to be held at the Centurion Club. The news comes just four months on since the player committed himself to the PGA Tour.
The current world number 13 is the biggest name to sign up for the competition despite the risk of sanctions from the PGA, which has not granted its members permission to play.
David Winkle, who is the agent for the 37-year-old, said in a statement: "Dustin has been contemplating the opportunity off-and-on for the past couple of years.
"Ultimately, he decided it was in his and his family's best interest to pursue it. Dustin has never had any issue with the PGA Tour and is grateful for all it has given him, but in the end, felt this was too compelling to pass up."
The winner of the inaugural event in Hertfordshire will claim £3million out of a prize pool which totals £20million.
Johnson will join the 48-man field which already includes the likes of Louis Oosthuizen, Branden Grace, Lee Westwood, Ian Poulter, Sergio Garcia, Kevin Na and Martin Kaymer.
The American had been scheduled to compete at the Canadian Open, which runs at the same time. However, he will now line up for the first of eight worldwide events organised by the LIV Series.
Canadian Open organisers announced on Twitter: "Together with our partners at RBC, we are disappointed to learn at this late stage that Dustin Johnson has made the decision to play the LIV Golf Event. As a past RBC Canadian Open champion, Canadian golf fans were looking forward to DJ's return this year."
Greg Norman, who is the chief executive at LIV Golf, hit back saying: "Free agency has finally come to golf. This is an opportunity to start a movement that will change the course of history by bringing new and open competition to the sport we all love.
"The desire shown by the players to participate in LIV Golf demonstrates their emphatic belief in our model and confidence in what we're building for the future."
Norman has been criticised for heading the breakaway tour, which is being backed by Saudi investors.
The LIV Golf Series will adopt a new format in a bid to make the sport more exciting for fans, with 12 teams of four players contesting in each three-round event to determine team and individual winners.
DP World Tour declined to comment on any possible sanctions for players who compete at Centurion after being denied the required release.