"I am not afraid to say this, I don't say we are going to win (the title next season)," Mourinho told newspapers on Sunday. "I cannot because there are top teams, top coaches, top managers in England."
"One thing I will promise. If you give me four years I will win the championship."
Chelsea have only lifted the championship once in their 99-year history, in 1955.
Mourinho, who last week replaced the sacked Claudio Ranieri at Stamford Bridge, wants to build his team around England midfielder Frank Lampard.
"I love Frank Lampard," said the former Porto manager. "He is the kind of player you want in modern football because he can adapt to anything."
"He has the type of qualities I want in a player. When I look back at my time with Porto, if someone had told me I could have Lampard in my team, he would have been straight in."