The forward passed a medical and agreed terms on Friday to seal a move to Stamford Bridge.
Bayern's signing of Italy striker Luca Toni from Fiorentina this week left Pizarro further down the pecking order at the Allianz Arena.
And he joins fellow Blues new-boy Steve Sidwell, who arrived at the Bridge from Reading last month.
Despite being a regular substitute for Bayern - behind Roy Makaay, Lukas Podolski and now Toni - Pizarro's availability prompted interest from a number of top clubs.
But the forward told Chelsea TV: "I think it's very important for me to win some titles and I have the chance here to win them.
"The most important thing is the Champions League which I was looking to win with Bayern, but we didn't have the chance.
"I think now we have a good team, a good trainer and the chance to win it.
"I had some interesting offers, but the most important thing was that I talked to the coach, I talked to the people here, and they were very interested. We have many chances to win titles here and that's what I want."
Pizarro added: "I get used very fast to playing with different kinds of players. I did it at Bayern and I don't think it will be a problem now."
The signing is Chelsea's second of the summer following the recruitment of Oldham starlet Danny Philliskirk.
Pizarro had been expected to put pen to paper on a four-year deal at Stamford Bridge with unsettled defender Khalid Boulahrouz tipped for a move in the opposite direction.
Boulahrouz has failed to settle in England following his £10million move from Hamburg last summer and would welcome a return to Germany.