Sources said Jackson was fined specifically for statements he made at a news conference last week about possibly hiring Fisher as Knicks coach.
The league's 30 teams were notified of the fine by league memo Monday afternoon, the sources said.
Among the reasons the league took this step, sources said, was to reinforce its annual reminders to teams of the league's anti-tampering rules, which prohibit teams from direct or indirect expressions of interest in other teams' impending free agents.
Jackson tweeted Wednesday that he was "undaunted" by the fine.
Undaunted by "stuff" we will continue to have a relationship with the press, which informs our fan base#chagrined
- Phil Jackson (@PhilJackson11) June 4, 2014
The Thunder were eliminated from the Western Conference finals on Saturday night. Fisher is widely expected to retire and told reporters after Oklahoma City's season ended that he plans to have conversations with teams about his future at some point.
Fisher just completed his 18th season. He played under Jackson with the Lakers, and helped that franchise win five NBA titles.
Information from The Associated Press was used in this report.