A league source told ESPNLosAngeles.com's Dave McMenamin that Fisher signed a one-year, $1.4 million contract with the team. It will be Fisher's 18th season in the league, and he enters it with the intention that it will be his last, the source said.
The 38-year-old Fisher has spent parts of the past two seasons with the Thunder, averaging 4.5 points in 44 regular-season games. He has averaged 7.1 points in 31 playoff games for them.
The five-time NBA champion with the Los Angeles Lakers has appeared in 240 postseason games.
Thunder general manager Sam Presti said in a statement: "Fisher has proven to be a valuable member of our team and we are excited to have him back.
"He has such a positive impact on his teammates and the organization."
Fisher is the president of the National Basketball Players Association.
Information from ESPNLosAngeles.com's Dave McMenamin and The Associated Press was used in this report.