The 27-year-old Frenchman impressed during a recent training match against Bristol Rovers and has done enough to impress manager Marc McGregor.
McGregor said: â€œPapis comes into what is currently a strong squad; he is looking to break into the team.
â€œHe is a good footballer and an athlete, which is what is needed at this level.
â€œHe is hungry to show us all what he can do moving forward.â€
Mendy last season signed for FC Drouais Dreux, who play in the French league Championnat National 3.
His other clubs include Les Ulis, Chauvigny, Chauray and Bayonne.
Weston host Welling United at the Woodspring Stadium tomorrow.