The 24-year-old Japanese forward joins the Lakers from the Washington Wizards, with Kendrick Nunn and three future second-round picks going the other way.
Hachimura is averaging 13.0 points on 48.8 per cent field shooting, with 4.3 rebounds and 1.2 assists per game this season.
He joins as Lakers side that has battled to remain in playoffs contention after a slow start, sitting at 22-25 prior to Tuesday’s game against the Los Angeles Clippers.
Lakers vice president of basketball operation and general manager Rob Pelinka was on hand to introduce Hachimura on Tuesday, outlining the reasoning behind the trade.
“(We) felt like it was an opportunity for us to strike early and address a need in a market that has proven to be a little bit slow,” Pelinka said.
“It doesn’t mean our work is finished: We’re going to continue to monitor the situation with the 29 other teams.
“Our job as a front office is always to look to improve our team both now and in the future, and we felt like Rui was the perfect way to do that, and that’s why we struck early.”
The Lakers are desperate to stay in contention with star LeBron James, 38, having inked a two-year extension in the offseason in the twilight of his career.
“The completely unwise thing to do would be to shoot a bullet early and then not have it later when you have a better championship move you can make,” Pelinka said.
“That’s a really delicate calculus and something the entire front office, we evaluate with all the moves.
“If we see a move that puts us as a frontrunner to get another championship here, the 18th one here, we’ll make it. And if that move doesn’t present itself, we’ll be smart and make it at a later time.”