The Nigerian had been with the Blues for over a decade, making 372 appearances, but has not featured under Antonio Conte this season.
The likes of Marseille and Valencia had been linked with Mikel but reports of Chinese interest emerged recently and the midfielder has opted for a switch to Tianjin TEDA.
In a message to the Chelsea fans on Twitter, the 29-year-old said: “I haven’t featured as much this season as I would have liked and I still have many years in the game ahead of me.
“With this in mind, I feel now is the time to seek a new challenge.
“I’m delighted to be joining Tianjin TEDA FC at a time that the Chinese Super League is really taking off, and I look forward to helping Tianjin TEDA FC continue to grow.
“To play in the Premier League is every professional player’s ambition.
“But to play for Chelsea, to become part of the Chelsea family to work with some of the best managers and players in the world, has truly been an honour.”
Chelsea take on Peterborough in the FA Cup on Sunday and they are 1/7 to come out on top.
A win for the League One outfit is priced at 18/1 and a draw is 9/1.