Smith fills the open spot left by rookie cornerback Johnny Adams, who was signed to the 53-man roster on Tuesday.
Between their active roster and practice squad, the Bills now have seven cornerbacks on their roster. Top cornerback Stephon Gilmore is out for several more weeks with a fractured wrist, while Ron Brooks is out for "some time," head coach Doug Marrone said, with a fractured foot.
Smith, who went undrafted in 2011 out of Arizona State, was in training camp with season with the Green Bay Packers. The 26-year-old has not appeared in a regular-season game.
Here's an updated look at the Bills' practice squad, which stands at the eight-player limit:
QB Thad Lewis
RB Ronnie Wingo
G/T Mark Asper
DL Izaan Cross
OLB Jamie Blatnick
CB Brandon Smith