The 24-year-old was a free agent after leaving Wigan Athletic this summer but completed his move to the Bundesliga outfit on Wednesday.
And the Argentina international has revealed that he asked former Chelsea team-mate Pizarro - who has had two spells at Bremen - for his advice ahead of agreeing the switch to Germany.
"I've been talking to Claudio about moving to Werder Bremen," Di Santo told Bild.
"I have learned the club has a very good reputation. Pizarro told me I should make the move and that I would find joy at the club. I am out to show what I am capable of."
Di Santo, who scored 13 times in 92 league appearances for Wigan, has signed a three-year deal with Bremen.