Bournemouth's Head of Football Operations Tiago Pinto said the decision to bring in Mandas was to add strength and quality to the Cherries' squad.
"He's shown his ability at the highest level with Lazio and the Greek national team. We're really excited about the impact he can make," Pinto told Bournemouth's website on Wednesday.
Mandas becomes the first Greek player to represent Bournemouth and will wear the number 29 shirt for Andoni Iraola's squad.
