Manager Nigel Adkins revealed the news following the Royals' pre-season draw with Yeovil.
"Jem Karacan was given the club captaincy last week," he said. "Jem is ready to step up and show the leadership qualities he's got within him. He's been at the football club since the Academy stages.
"He's come through the system and played in the first team, he's demonstrated he's got the ability that is required to be a leader of a group of people. He's got a feel for this football club, he knows what is required and now I want him to step up and lead."
Karacan, 25, was delighted with the news, tweeting: "Honoured to be announced new Reading FC captain! Looking forward to the new season & can't wait to get back playing!
"Thanks for all the messages and support it's much appreciated see you at the mad stad soon!"