A deal worth 75 million pounds, including transfer fee and salary, was finalized at a meeting in London less than 24 hours after Costa's penalty inspired Atletico Madrid's 3-1 Champions League win over the Blues on Wednesday.
Chelsea will pay around £35 million for the striker, although a significant portion of the transfer fee includes agents' fees.
The Europa League champion will also more than triple the wages of Costa, who is believed to earn around £50,000 per week at the Estadio Vicente Calderon. Chelsea is set to hand the 25-year-old a five-year contract worth £150,000 a week.
