Bru, who has played in the lower divisions in France and Portugal, was born in France and represented that country at underage level.
But he was able to play senior football for Mauritius because his parents were born in the African island nation.
He has played nine times for the Mauritius national team and joins the Victory on a two-year deal.
Victory coach Ange Postecoglou has made signing a defensive midfielder his top priority, and believes Bru can make an immediate impact.
"Jonathan looks to be the ideal fit for our squad, especially considering the array of attacking options we have," Postecoglou said.
"To have represented France at five different age levels speaks volumes about his ability."
Bru joins Spase Dilevski, Sam Gallagher and Adama Traore as Melbourne Victory's off-season signings.
He will link up with his new teammates next month.