The Leesiders have completed the signing of the former Republic of Ireland under 21 international ahead of the forthcoming 2013 season
The 24-year-old defender began his career at Everton, before joining Cardiff City in 2008. He enjoyed loan spells with Hereford United and Gillingham before opting to join Barnet in 2010.
Speaking to the club's official website, Dennehy said that he was 'delighted' to have joined Cork City.
"I'm delighted to have signed; I’m looking forward to getting into training and getting to know the lads," he said.
Cork boss Tommy Dunne said that Dennehy, whose brother Billy has previously played for Cork, represents 'a good addition' to his squad.
"Darren is an experienced player and, being from Tralee, is relatively local also," Dunne told corkcityfc.net.
"I have seen him play myself previously with the Irish under 21s, and he impressed me. He is a good addition to the squad and I believe his signing will strengthen the team, so I am delighted to have him on board."
Meanwhile, the Leesiders have also announced the re-signing of 33-year-old defender Neal Horgan, who has agreed to extend his deal with the club for the 2013 season.