Craig Kieswetter has agreed a new deal with Somerset until the end of 2014.
The 24-year-old England wicketkeeper-batsman has also decided not to take part in the Indian Premier League, meaning he will be available for his county for the whole of next season.
"It's superb news for his own personal development and the progress of Somerset," director of cricket Brian Rose told BBC Somerset.
South Africa-born Kieswetter made his first-class debut for Somerset in 2007.
He averaged 57 in nine CB40 innings last season, including two centuries, and has shown his worth in England's one-day set up, scoring 72 not out against Sri Lanka in July and 63 against India in October.
"I am delighted to extend my time at Somerset where I have been since I was 17 years old," said Kieswetter.
"To have come over and be associated with Somerset with the way that they are developing and continually challenging for everything on the county circuit is something that I am proud of.
"I hold the club very dear to my heart and I want to be part of the success in the future so I am delighted and very humbled to extend my stay."
Commenting on Kieswetter's decision not to compete in the IPL next season, Rose added: "For his age and connections, I think it's a very clever decision.
"He needs to put Matt Prior [England wicketkeeper] under the kosh and develop his own test career and to do that he's got to get first-class hundreds, so he's got to play county cricket."