The 24-year-old was a free agent after leaving Wigan Athletic and completed his move to the Bundesliga outfit on Wednesday.
And the Argentina international revealed that he asked former Chelsea team-mate Pizarro, who has had two spells playing for 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 in Bremen.