Johnson signed a contract yesterday to play for the rest of the season for a reported $2.5m (pounds 1.6m) and sold his five per cent share in the club, as required by National Basketball Association rules.
Johnson, 36, led the Lakers to five NBA championships in the 1980s. He retired in November 1991 after announcing that he had tested HIV-positive, although he went on to lead the United States Olympic "Dream Team" in 1992.
The 6ft 9in Johnson, three times named the NBA's Most Valuable Player, returned to the sport because he wanted his three-year-old son, Earvin III, to see him play, he has said.
His comeback, against Golden State Warriors, promises to be a media sensation. Johnson was mobbed by reporters when he arrived at practice yesterday with a broad smile on his face.
"Yes, I am back, and I'll see you guys later," he said. "Hey, I'm back. It's that time. I have to go to work." Last summer, Johnson said he would "never" return.
The signing of the contract was delayed as he apparently struggled with whether to put a successful business career on hold and risk discrediting his own legend. Johnson opened the Magic Johnson Movie Theatre last year, a hi-tech 12-screen complex at a shopping centre in South-Central Los Angeles, a tough neighbourhood devastated in the 1992 riots. Its phenomenal success - since its opening it has ranked in the top five of 22,000 cinemas nationwide in sales - has held up Johnson locally as a new star of black entrepreneurship.
Johnson weighs in at 250lb, 25lb more than when he last played for the Lakers, and has been playing mostly in exhibition games. Although it was unclear what position he would play, his team-mates said he brings a winner's attitude and would boost the attendances for a team that has suffered a mixed record since he left.
"He adds so much," Sedale Threatt, the Lakers guard, said. "He can play five positions. I think teams will have to concentrate on him, and with the nucleus we already have it will make us the best team in the West."
After the game today, Johnson could face another NBA legend, Michael Jordan, when the Lakers play the Chicago Bulls on Friday. Another member of the Lakers, Cedric Ceballos, said Johnson wanted to play today to "warm himself up for Michael Jordan."