Jackson was in attendance for the Ohio St-Nebraska game last Thursday night and told Cleveland.com that Russell was a "great looking kid" and a "great prospect."
NBA spokesman Tim Frank confirmed the fine Tuesday night but did not disclose the amount.
Team personnel are prohibited from publicly discussing players who aren't yet eligible for the NBA draft.
This isn't the first time Jackson has been punished by the league for his public comments. Last season he was fined $250,000 for prematurely stating Derek Fisher was a head coaching candidate while he was still playing for the Oklahoma City Thunder.