Coach Mike D'Antoni confirmed the decision Thursday after saying earlier this month that he doubted that Nash, 40, would return after being plagued by nerve-root irritation in his left leg much of the season.
"He's not going to play," D'Antoni told reporters, according to the Los Angeles Times. "It doesn't make any sense for him to come back for 15 games, whatever."
The two-time league MVP averaged 7.6 points and 4.7 assists in 10 games this season while shooting just 36 percent from the floor and 31.6 percent from 3 -- well below his career marks of 14.3 points, 8.5 assists, 49 percent shooting and 42.8 percent from deep.
An 18-year veteran, Nash was noncommittal about his chances of playing again this season when asked earlier this month.
"We'll see," he said. "I couldn't really make a prediction. If I get the chance, it would be great."
Nash's shutdown came one day after the Lakers ruled Kobe Bryant (knee) out for the rest of the season.
Information from ESPNLosAngels.com's Dave McMenamin was used in this report.