Terms of the deal with the 38-year-old Fisher were not disclosed by the Thunder, whose 41-15 record is second only to the San Antonio Spurs (45-13) in the West.
Fisher, president of the National Basketball Players Association (NBPA), had been idle since being released last December by the Dallas Mavericks.
"We are excited to welcome Derek back to the Thunder organization," said general manager Sam Presti. "He contributed to our team in various ways last season, and we are looking forward to him joining us again."
Fisher, in his 17th NBA season and a five-time NBA champion with the Los Angeles Lakers, appeared in 20 regular season games with Oklahoma City last season after signing in March and averaged 4.9 points and 1.4 assists in 20.4 minutes per game.
In 20 playoff games, he averaged 6.3 points and 1.3 assists in 22.3 minutes per game as he helped Oklahoma City reach the NBA Finals against the Miami Heat.
Fisher was not re-signed by the Thunder in the off-season and played nine games with Dallas this season before suffering a knee injury and asking the Mavericks in December to release him so he could spend more time with his family.
- Sports & Recreation
- Dallas Mavericks