The club have been without a 'keeper for the whole of pre-season after number one Matt Gilks left for Barclays Premier League side Burnley.
Lewis told the club's official website, www.blackpoolfc.co.uk: "I was sat at Cardiff for the last two seasons behind David Marshall, who has done outstanding.
"I've had to make do with a couple of cup games and the odd league game here and there, and it was pretty frustrating really
I knew that I had to get out and play some regular football.
"It's great to come to a club like Blackpool and hopefully make the number one position my own."
The 26-year-old has a wealth of experience, with over 200 appearances since coming through the academy at Norwich
He has since played for Stockport, Morecambe and Peterborough, before transferring to the Bluebirds in 2012 for £400,000
Lewis has joined on an initial loan with a view to a permanent deal
The terms of the deal this season mean he cannot play against parent club Cardiff
The Tangerines have made a flurry of signings in recent weeks after just eight professionals turned up to pre-season training, with more than 20 players leaving the club
Jose Riga's men begin their Championship campaign at the weekend against Nottingham Forest.
Source : PA
Source: PA