Having announced his retirement after Brisbane Roar's elimination final defeat to Melbourne City, Khalfallah's signing with the third tier team comes as a surprise.
“I just want to stop now, I don’t want to play anymore," Khalfallah said to Fox Sports after the loss 2-0 on April 20.
"I enjoyed it, I loved it and that's it. Sometimes it’s time to stop and do something else so we’ll see."
Khalfallah has appeared in 100 A-League matches, scoring 13 goals while providing 18 assists, winning the Championship/Premiership double with Melbourne Victory in 2015, a season in which he was named in the PFA Team of the Season.
Khalfallah has already made his first appearance for his new side, a goalless draw against Eastern Lions.
Nunawading currently sits at the bottom of the Victoria East Conference with two wins from 12 games.