David Murphy will remain at Birmingham for a further two years after an extension clause in his contract was activated.
The reliable left-back has been one of the Blues' top performers this season having dislodged Liam Ridgewell at the start of the campaign, making 46 appearances in all competitions and scoring six goals.
Murphy, 28, joined the midlands club from Hibernian in January 2008 and is now contracted until 2014.
Young striker Jake Jervis has been offered a new one-year deal, fellow promising centre-back Jack Deaman has been given six-month terms while manager Chris Hughton has also promoted a handful of Academy players to the professional ranks.
But out-of-contract quintet Caleb Folan, Enric Valles, Cian Hughton, Ashley Sammons and Luke Hubbins have all been released and are free to find new clubs.
Talks continue with veteran captain Stephen Carr and goalkeeper Colin Doyle over their futures.