The deal will keep the 24-year old at Members Equity Stadium until the end of the 2010/2011 season.
"I have been very happy in Perth and I see a great future for the club and wanted to be part of that," Pellegrino told the league’s official website.
"We're definitely on the improve, you know it's always difficult when a new squad of players come in but we're working well now and hopefully we can keep the group together and continue to build on what we've started.
"I had a great feeling from the first moment I joined the club and set myself to be here for the long haul. We have plenty of good things to look forward to and who knows I might even be able to play out the rest of my career here."