The veteran shot-stopper is thrilled to have committed his future to the Nerazzurri and insisted that the entire team is supporting coach Andrea Stramaccioni
The 37-year-old, who has added one more year to his previous deal, has been at San Siro since 2010, when he joined the Nerazzurri from Sampdoria.
He still does not know whether he will be Inter's second or third-choice custodian for the new season following the club's signing of Samir Handanovic, but is delighted to have prolonged his stay with the club.
"I am very happy to have signed a new deal, especially because I am no longer a young player," Castellazzi told Inter Channel. "This is a sign that the club liked my performances.
"We are working very hard these days with the right mentality. We are all at the disposal of coach Andrea Stramaccioni, trying to follow all his instructions, step by step."
Castellazzi made 11 appearances in all competitions last season, conceding 21 goals.