The 20-year-old Nigeria international spent the latter part of the 2013-14 campaign on loan at the Riverside Stadium, making 14 Championship appearances after arriving in January.
Omeruo subsequently played in all four of his country's matches at the World Cup in Brazil as they exited at the group stage, and he has clearly done enough to convince Middlesbrough head coach Aitor Karanka of his quality.
Posting on his official Twitter account on Sunday, the centre-back suggested that a move back to the club had been agreed.
He wrote: "Holiday is finished.. Almost time for work again.. happy to be rejoining boro for a new season."
Omeruo had previously stated his desire to continue working under Karanka, telling the Evening Gazette earlier this month: "My time at Middlesbrough was one of the best experiences I've had in football and I enjoyed every moment of my time at the club.
"The Boro fans are amazing and I was impressed with the support they showed the team every week.
"I would like to return to Boro on loan but it's not in my hands."
Omeruo joined Chelsea in 2012 from Belgian club Standard Liege and spent time on loan at Dutch side Den Haag in 2012-13.
He agreed a new long-term contract with Chelsea prior to his departure for the World Cup that will keep him at Stamford Bridge until 2018.
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