Sources told ESPN.com that the Thunder, after trading Eric Maynor away last week before the NBA's trade deadline, have made plans to sign Fisher, who joined Oklahoma City for the stretch run in March 2012 after the Los Angeles Lakers dealt Fisher to Houston.
The veteran guard will sign with the team Monday for the remainder of the season, according to multiple league sources.
The Thunder declined comment late Sunday.
Fisher appeared in nine games this season with the Dallas Mavericks before asking for his release in December because the 38-year-old -- after suffering a knee injury -- wanted to return home to his family in Los Angeles.
Fisher, who won five championships with the Lakers, was viewed as a key locker room presence by Oklahoma City coach Scott Brooks as the Thunder made it all the way to the Finals, losing to the Miami Heat in five games.
In recent weeks, Fisher -- who doubles as NBA Players Association president -- has been working out of the NBPA offices in advance of the player vote during All-Star Weekend to oust union chief Billy Hunter.
Fisher was productive during his brief stint in Dallas, averaging 8.6 points and 3.6 assists in just more than 25 minutes per game. And he was a natural fit in the Oklahoma City locker room last spring, delivering valuable championship experience to a team short on playoff-tested veterans.
Upon his release from the Mavericks in December, Fisher said: "The recovery time [from the knee injury] will be approximately two weeks. With this news and the difficulty I have been having being away from my family, I have asked the organization to waive me so I can return home.
"[Mavericks owner] Mark Cuban has been extremely supportive and has granted me this request. I cannot say enough good things about this organization. From Mark, to Coach [Rick] Carlisle, to the players on the Mavericks' team, I sincerely thank them for the opportunity.
"I have made decisions in the past, leaving money and opportunity on the table, and I will need to do that again. My family is my priority and that is where I choose to be. I won't close the possibility that I will play again; however, for now my family and being close to them remains the priority."
ESPNLosAngeles.com's Ramona Shelburne contributed to this report.