The 29-year-old left-back managed only six games as Palermo were relegated in the 2012-13 campaign but, after making a full recovery from ligament damage, he has moved to the Stadio Renato Dall'Ara to bolster coach Stefano Pioli's defensive options.
The Rossoblu coach's decision to sign a new defender comes as no surprise after Bologna were beaten 3-0 at Napoli on the first weekend - the largest margin of defeat across 10 opening games.
But Mantovani feels he can help shore up the back four, should he contribute in Sunday's visit of Sampdoria.
He told Bologna's official website: "I know Pioli is a great coach and a good person, I definitely know what to expect from the team and what will be asked of me.
"I can play in various roles in different positions and I hope to be useful to Bologna.
"It was always my intention to get straight back into Serie A and as soon as the call came from this big club I accepted immediately.
"There are all the ingredients here for us to do well and it will be a very exciting challenge for me."
Archimede Morleo, Niccolo Cherubin and Fredrik Sorensen are unavailable through injury but Pioli received a further boost this week after playmaker Alessandro Diamanti extended his contract until 2018.
Sampdoria boss Delio Rossi, while being reasonably satisfied with the team after watching a narrow 1-0 loss to Juventus on the opening day, has asked his forward line to step up.
"I don't think strikers should be judged by how many goals they score but by how they cope in certain situations," he said.
"I think our strikers will surely do well in pursuit of our objectives."
Midfielder Pedro Obiang is injured and defender Paolo Castellini is suspended in Bologna, where Samp have failed to win since November 2003, having played out three consecutive 1-1 draws in recent seasons.