The move will give the highly-rated 21 year old valuable experience of first team football.
Manager Sean O’Driscoll explained: “Karl is a young ‘keeper who we think has a bright future.
“But at this stage in his development he needs to play some games so we’re happy for him to go to Walsall where we know he will be well looked after and get some good first team experience in League One.
“If we need goalkeeping cover during his time at Walsall we will be able to utilise the loan market to bring in a ‘keeper or in an emergency recall Karl from his loan.”
Darlow has made two appearances for The Reds as understudy to Lee Camp but played eight times last season for Newport County in the Blue Square Premier Division.
He is poised to make his debut for Dean Smith’s Walsall against Preston tomorrow.