Carberry had struggled to break into Surrey's all-star line-up, playing in only one championship match last season.
He did however, manage to notch his maiden first-class century against Cambridge University at Fenner's.
The left-hander's previous first-class best of 84 came against Glamorgan at Cardiff in 2001.
Key task
Kent's skipper David Fulton commented: "Rob Key had a good winter with England in Australia and we very much hope that his progress with England continues this summer.
"However, it is possible that we might be without him for a number of matches and we want to ensure that we have the batting back-up should this happen."
The county have also confirmed that batsman Matthew Banes has re-signed for this season after a series of good performances in Australia grade cricket.
Kent are still short of one overseas player for next season but are unlikely to make a new signing until the World Cup in South Africa has finished.