The former Catania striker signed a three-year contract for an undisclosed fee, but believed to be Â€3m plus performance-related bonuses.
"I chose Sampdoria because I think this is a strong side, Sinisa Mihajlovic and President Massimo Ferrero really wanted me and it's a great club," said Bergessio.
"I am happy to be here, as it is important for a player to feel loved. Ferrero put his faith in me, I hope to repay it and thank all the fans who wanted me here.
"I don't want to talk about statistics, but it would be important for me and for Sampdoria to score 10 or more goals this season."
Bergessio will wear the number 18 jersey because "I wore it at international level."
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