The 22-year-old winger, who is on a season long loan at Blues from Arsenal, was released on parole on Thursday morning having served thirty days at Woodhill Prison in Milton Keynes.
It is not yet known when Pennant will be able to play football as part of his parole conditions state that he will have to wear an electronic tag.
Pennant Released
"It's a relief to be out, I'm looking forward to putting on my football boots and start training again," Penannt said in a short statement.
"I'd like to thank all those that have helped me through this difficult period and I'll be making further statements in due course."