The defender, 25, has signed a one-year deal at Oakwell and will go straight into Keith Hill's squad for Tuesday night's game at Wolves.
"I'm delighted to have signed for Barnsley," Cranie told the club's official website.
"It's taken up to the start of the season to get it done, but I'm glad I'm here now.
"The gaffer has shown a lot of faith in me and when I came in to have a look around he had a lot of good things to say.
"I've been at Leeds training during pre-season so I'm fit and raring to go.
"The game at Wolves will be a tough one, but the lads are all positive.
"On the Saturday they played very well and they deserved to win, which is a great positive to take into Tuesday's game."
Cranie, who made several appearances for Leeds during pre-season, began his career at Southampton, moved on to Portsmouth on a free transfer in 2007 and in 2009 was signed for an undisclosed fee by Coventry, where he made 120 appearances.