The Polish striker, signed from Bayern Munich for around 50 million euros, was formally introduced as a Barca player alongside club president Joan Laporta.
The unveiling came a day after the La Liga side started their four match tour of the United States with a 6-0 win over David Beckham’s Inter Miami.
Lewandowski, 33, who left the German champions under a cloud after a dispute over a new contract as well as clashing with coach Julian Nagelsmann over tactical choices, cannot wait to get started.
Lewandowski joined Bayern in 2014, scoring 344 goals in 375 competitive matches and broke the Bundesliga’s single-season scoring record.
But he could make his Barca debut in Las Vegas this weekend against arch-rivals Real Madrid and said: “We worked hard to get to this moment but we got there in the end.
“I am always hungry to succeed and have the winning mentality. This is a new challenge for me and I have already seen this is a squad with huge potential.
“There is a lot of quality and I want to do my best for the club. I am ready.”
Lewandowski joins Barcelona in the midst of a financial crisis yet although the club have racked up debts of almost one billion euros, the striker becomes the club’s fourth summer transfer after the signings of Ivory Coast midfielder Franck Kessie from AC Milan, Chelsea defender Andreas Christensen on a free transfer, and Brazil winger Raphinha.
“We are doing our best to restructure,” said Laporta. “We did a lot of work to make this happen.
“There is a big expectation for you (Lewandowski). You are a football star.”