The 22-year-old winger, on loan at Blues from Arsenal, pleaded guilty to two charges of drink-driving and driving without insurance when he appeared at Aylesbury Magistrates Court last month.
Sentencing was deferred until today (March 1st) and he was handed a three-month jail term and banned from driving for three-years. His lawyers are to appeal the custodial sentence.
Blues are still committed to keeping the former England Under 21 international on a season long loan deal and chairman David Gold stated last week that whatever sentence that Pennant received, it will not affect Blues wanting to sign him on a permanent contract at the end of the season.