In June, George told the Pacers he planned to opt out of his contract in 2018, when he wanted to sign a free agent deal.
"At the request of the Indiana Pacers, the NBA opened an investigation into alleged tampering by the Los Angeles Lakers," the league said in a statement from spokesman Mike Bass.
"The independent investigation is being conducted by the law firm Wachtell, Lipton, Rosen & Katz."
"The Lakers have been cooperative and, at this point, no findings have been made. We have asked both teams to refrain from commenting while the investigation is ongoing," the league said.
In June, George told the Pacers he planned to opt out of his contract in 2018, when he wanted to sign a free agent deal with the Lakers that would bring him back to his native California.
On June 30, the Pacers traded him to the Oklahoma City Thunder.
ESPN reported that the league is investigating whether Magic Johnson, the former Lakers star who is now president of basketball operations for the club, had improper contact with George.
Johnson said on a television chat show in April that he would love to see George in a Lakers uniform.
The league's rules against tampering forbid teams from trying to influence players under contract to other teams, allowing them to try to lure players only when they become free agents on July 1 of the year their contracts expire.
The Lakers had little to say about the charges on Sunday, but insisted they feel they did nothing wrong.
"As the NBA's statement made clear, we cannot comment about the specifics of any ongoing investigation," said Lakers spokesperson Alison Bogli.
"We can confirm, however, that we are cooperating fully with the NBA in the hope of clearing our name as soon as possible."
George, 27, averaged 23.7 points and 6.6 rebounds per game last season for Indiana.