Middlesbrough-born Liddle, a product of his hometown club's youth system, can play in defence or midfield and has made over six-hundred career appearances during spells with clubs such as Hartlepool United, Notts County, Bradford City, Chesterfield and Carlisle United.
The 33-year-old will add some vital experience to the Saddlers' defensive unit whilst also offering plenty of wisdom for the club's younger players as they look to make their way into the game.
Speaking via the club's official website, Gary said; "I am thrilled to be here. Darrell was the first person who called me when I was on holiday and, even though it has taken a little bit longer, I am glad it’s sorted now.
"I had a few phone calls from different managers but it’s always nice to have a call very early on. It shows their desire and that they want to bring you in.
"Plenty of managers say the right things but you don’t always get a contract offer. Darrell put his cards on the table from the off and I am looking forward to working with him.
"I have played in a few different positions and started off as a midfielder but I can also drop back into defence. I have made over 600 appearances in my career for five clubs and I have always given 100% no matter where I am."