The 31-year-old left-armer was released by Sussex in September having been at Hove since 2006.
The ex-Leicestershire paceman has taken 34 first-class wickets at an average of 51.05, 79 one-day scalps at 29.22 and 82 T20 wickets at 23.90.
"It's great to have Chris on board," said Gloucestershire head coach Richard Dawson.
Middlesbrough-born Liddle also played for Dhaka Gladiators in the Bangladesh Premier League in 2013.
"He's got a lot of experience in one-day and T20 cricket, having performed strongly for Sussex and he will add excellent competition to our bowling unit," added Dawson.
"It's a great opportunity for him to come here and compete in all formats of the game as he has a lot of potential in Championship cricket. We are all looking forward to him joining up with the lads."
Gloucestershire have signed former Sussex seam bowler Chris Liddle on a two-year contract.