As per Major League Soccer and club policy, details of the deal were not disclosed.
Pisanu, who will turn 31 on Monday, joins the Impact following a trial with the team during its post-season camp in Italy last November.
"We are very pleased to have been able to come to a loan agreement with Bologna," said Impact sporting director Nick De Santis. "Andrea can play behind the forward or as a wide player. We are adding another player with good offensive qualities who has a good understanding of the game. We are excited to bring in another first division player who is extremely motivated to come to MLS, and more importantly he will start the training camp from day one with the team. This will put him in a better situation to adapt to his teammates and to the style of soccer the team plays."