The Chelsea star's father had last been seen in the Nigerian city of Jos on August 12, but was discovered alive in the town of Kano on Monday.
Michael Obi, manager of a transport company, told the BBC that he was "very stressed" after his horrific ordeal, which left him bruised and battered from beatings that were administered to him in captivity.
The kidnappers are reportedly in police custody, while Desmond Agwu, director of the local State Security Service, confirmed the news of Mikel's release.
"Yes, he has been found and is currently at a Police Station in Kano," he said.
The 24-year-old Chelsea star's management group SEM also confirmed the news.
"Earlier today Michael Obi called his family to advise them that he had been released by his abductors," it said in a statement.
"SEM have waited until now to release this information, to ensure that Michael was safe.
"John Obi Mikel would like to thank everyone in Nigeria, his family and friends, Chelsea FC and their fans and his agents for their total support during this terrible time."
The Nigeria international played in Chelsea's opening fixture of the Premier League season at the weekend just hours after being told the news of his father's abduction, with subsequent reports claiming that a ransom of up to £80,000 had been demanded.