Chilvers had a loan spell at Vale Park last season when he was on the books at Notts County, making 12 appearances for the Burslem outfit.
Vale were unable to make a move for the 31-year-old when he was released by the Magpies as they were in administration.
Manager Micky Adams told the club's official website: "After a frustrating spell, we are now in the position where we can bring in new players and I thank the new owners for allowing us to act swiftly to do that.
"We know from working with Liam previously that he will add a calm and experienced head to the defence, having played for the majority of his career in a higher division.
"He also knows the club and our aspirations and I, along with the rest of the staff and players, are looking forward to working with him until the new year."
Centre-half Chilvers will stay with the Valiants until January 5, 2013 and will go straight into the squad for this weekend's League Two fixture away at Aldershot.