The 30-year-old Lithuania centre-back, who spent seven years in Scotland with Hearts, has signed a two-year contract and will join the club's pre-season tour of North America.
Zaliukas turned down the offer of a Rangers deal last September and later joined Leeds United, who released him at the end of last season.
He is the second new centre-back to arrive this summer following the signing of Darren McGregor, while Kenny Miller and Kris Boyd have also joined.
Goalkeeper Steve Simonsen, 35, has also signed on to be Cammy Bell's deputy for a further year, and he told the club website: "I had a lot of other teams getting in contact and it was a little bit like buses this summer.
“A few in England and Scotland got in touch but as soon as the manager expressed his interest in bringing me back here again it was a non-competition.
“This was the only place I wanted to come to and there’s massive appeal here because I thoroughly enjoyed it at Rangers last season."