The left back joins John Hackworth's side on a free transfer after parting ways with Sydney FC.
Fabinho, who began his career in Brazil with Londrina, left A-League club Sydney FC in April in search of consistent first-team playing time, and he joins the Union to battle for the starting left back spot with sophomore defender Ray Gaddis, a converted right-sided defender who has been deployed almost exclusively on the left this season.
The Brazilian's impending arrival was leaked early by the player on Thursday, when he tweeted "Happy with my new club, Philadelphia Union! (MLS), looking fwd to playing soon." That message and another on Facebook were later deleted, but the Union confirmed the signing with an official announcement of their own.
“Fabinho has had a successful career and we’re excited to add someone of his caliber,” said Union manager John Hackworth in a team statement. “We think he can provide good depth and quality to an area of our team where we were a little thin.”
Fabinho will be eligible to play when Major League Soccer's international transfer window opens on July 9, menaing his first match could be against Chivas USA three days later.