The Porto ace claims talks with The Premiership big spenders are at an advanced stage and he expects to tie up a deal after the European Championship.
New Chelsea manager Mourinho is keen to bring some of his former Porto stars to West London and he has already agreed a deal for full back Paulo Ferreira.
Deco admitted after Portugal's 2-0 win over Russia that a deal was close to completion.
"The things between the FC Porto and Chelsea are practically all decided, but I will only think about this after the European Championship," said Deco.
"I still have to take the medical examinations and sign a contract."
The Brazilian-born ace admitted that Chelsea meet his ambitions to be successful and that was his main reason to leave Porto.
"My will as I have already said previously is to continue my career in a club that gives conditions to me that FC Porto gave me all these years to fulfil my objectives," he added.
"Perhaps Chelsea is one of these clubs."
Deco and Ferreira could be joined by club and international team-mate Costinha at Chelsea, but the midfielder admits that a number of other clubs are interested in his services.
Mourinho is a big fan of Costinha and wants to bring him to Stamford Bridge, but they could face a fight for him as several other sides are tracking the former Monaco man.
"They say that I will follow Deco but nothing it is concluded and it seems that there is other interested clubs," said Costinha.
Meanwhile, Joel Kitamirike has left Stamford Bridge after failing to establish himself in the first team.
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