The charge for the 26-year-old Morocco global, who will see out the battle in Amsterdam, could ascend to £36.7m contingent upon additional items.
Ziyech was one of Frank Lampard’s top focuses during the January move window yet Ajax would not sell one of their key players mid-season.
A Chelsea articulation read:
“Chelsea Football Club has reached an agreement with Ajax to sign Hakim Ziyech this summer.
“The move is subject to the player agreeing personal terms and he will remain at the Dutch club for the rest of this season.”
Ziyech has eight objectives and 21 aids 30 games for Ajax this battle, which has helped them to the highest point of the table.
He joined the club from FC Twente in 2016 and just marked another three-year bargain the previous summer.