Michael Obi, the father of Mikel John Obi, who also has played for the Nigerian national team, had last been seen Aug. 12 in Jos. The father told the BBC he had been kidnapped in Jos before being transferred to Kano.
"I am very stressed," he said.
His kidnappers were in custody in Kano in northern Nigeria, officials said.
The British broadcaster reported his face had shown evidence of having been beaten.
Vanguard had reported members of the Obi family denied Friday reports the abductors had demanded more than $130,000 ransom.
On Monday, the player's management company, Sports Entertainment & Media Group, issued a statement saying: "Earlier today Michael Obi called his family to advise them that he had been released by his abductors. SEM have waited until now to release this information, to ensure that Michael was safe."
The statement said the 24-year-old midfielder extended his thanks to family, friends, fans and others "for their total support during this terrible time."
He had continued playing for Chelsea since his father's kidnapping.
"I wouldn't want to let the club down and if I didn't play that game I think my mum would be very sad," he said.
Chelsea manager Andre Villas-Boas had praised the star's "amazing mental toughness" on Friday.