The deal will see the 29-year-old play at nib Stadium for the rest of the season with an option for a permanant move in the 2014-15 A-League campaign.
Sernas will give interim coach Kenny Lowe yet another option in what is already a potent final third which boasts the likes of Shane Smeltz, Jamie Maclaren and Sidnei, with the arrival of the pacey striker exciting the Glory caretaker.
"Davydas Sernas is a proven goal scorer who can play anywhere up front. His all-action style of play should suit the Hyundai A-League and will quickly make him a fans' favourite," Lowe said.
The Lithuanian international has represented his country 35 times for a return of five goals, including strikes against Spain and the Czech Republic, while he has also enjoyed a solid career across Europe which has seen him score 69 career goals.
His most prolific spell came at Polish side Widzew Lodz where he found the back of the net 30 times in 68 games.
Sernas was snapped up after passing a medical in Perth on Friday and the club has confirmed he will be available for selection for the Glory's home game against Melbourne Victory on January 31.
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