The highly coveted forward, who is renowned for being quick and direct, has been linked with a string of Premiership clubs in the last year, including Tottenham, Fulham, Charlton and Liverpool, after growing increasingly disenchanted in Holland.
He has been outspoken about needing a new challenge and playing at a club where he is guaranteed Champions League football.
Chelsea's capture of Kezman will be a big boost coming days after Steven Gerrard's dramatic U-turn over his move to Stamford Bridge.
Chelsea needed to strengthen their frontline after they released Jimmy-Floyd Hasselbaink on a free transfer this week.
But the Serbian is not considered a direct replacement for Hasselbaink and new manager Jose Mourinho is expected to use the money at his disposal to buy another proven striker.
There continues to be speculation linking Real Madrid's Fernando Morientes to Chelsea. Either Adrian Mutu or Hernan Crespo, both of whom had disappointing first seasons at Stamford Bridge, could still be released to make way for a new addition.
Iceland striker Eidur Gudjohnsen is the only current Chelsea forward guaranteed to be at the club at the start of next season.
Chelsea are also still looking to add a midfield player and a centre back to their squad.
