The long-time Blue left Burton Albion at the end of last season.
Blackman has joined Shrewsbury on a short-term deal.
Shrewsbury manager Gareth Ainsworth said: “Jamal Blackman has come in as my first signing on a short-term contract.
“We have conceded way too many goals under me so far.
“But that is not an indictment on any keeper, that’s just 'Can we strengthen?' There are all sorts of reasons why we have conceded.
"Jamal will strengthen us. I like carrying three keepers anyway.
“And he'll start today. He’s a huge talent who has been at some big clubs.
“He’s lost his way a little bit. I know we are going to have to be patient with him, but I can get him back to his best – without a shadow of a doubt.
“He is imposing when he is in that goal and hopefully, today, that is what he will be to the Wigan players.”
Blackman made his debut in Saturday's 2-2 draw with Wigan Athletic.