Staff at Ashton Burkinshaw picked up the award at a ceremony at the five-star Marriott Hotel in London's Mayfair, attended by representatives from 300 estate and letting agents in the country.
The Estate and Letting Agent Awards 2009 scheme was sponsored by the Property Search Group, and Globrix.com and was supported by the Royal Institution of Chartered Surveyors.
Manager of the Crowborough branch Fenella Blamey said: "Winning this award is a fantastic achievement for everyone at Ashton Burkinshaw."
She added: "We pride ourselves on our outstanding levels of customer service and these awards are a reflection of our hard work. Unlike other awards, this award gives customers a voice and is based entirely on their votes."
The results of the competition were determined by research carried out with customers at the Crowborough branch who were asked questions about the service they received from the agent