The Yorkshire club hope to complete a medical today, subject to a few final details. They have seen off competition from AFC Wimbledon to sign the 19-year-old.
Simons recently penned a new contract at Stamford Bridge until 2023, with the club holding an option to extend the deal by another year.
The renewal came as a relief within the Chelsea academy after he snubbed transfer interest from Watford, Norwich, Southampton and Brighton with his old deal due to expire this summer.
Now, with the Blues having signed academy midfielders Carney Chukwuemeka and Cesare Casadei for a combined £33million, they have opted to loan out their homegrown talent.
Simons will join an ambitious Hull side who are targeting promotion under new ownership this season. He will link up with Nathan Baxter, who is one of the most talented goalkeepers in Chelsea’s academy and also currently on loan at MKM Stadium.
Simons will be one of the few Cobham academy graduates allowed out on loan this season as director Neil Bath targets a competitive campaign at youth level.
Chelsea’s under-21s side were almost relegated last season but were saved by a last-minute goal against rivals Tottenham.
The 2021-22 campaign was a good one for Simons, as he made his senior debut by starting in the Carabao Cup match against Brentford in December. He also was often given the captain’s armband within Chelsea’s development squad.