Andy Taylor has signed a one-year deal with Walsall after joining on non-contract terms earlier this week.
The 26-year-old defender appeared in the Saddlers' 3-0 defeat at QPR in the Capital One Cup, and impressed enough to be handed a permanent deal.
The defender was released by Sheffield United earlier this summer, where injury restricted him to 45 appearances in three years.
"Andy did really well for us at Loftus Road," Saddlers boss Dean Smith said.
"He's an attacking full-back who fits in with the way we are trying to do things here and it's a real boost to have him on board."