The chocolate company struck up a deal with Let's Buy British Imports to stop imports of Cadbury products made overseas, reports Tatiana Schlossberg at The New York Times.
The company will also stop importing British Kit Kat bars, Toffee Crisps, and Yorkie chocolate bars.
Fans of chocolate manufactured in Britain say it tastes better than the American-made version.
A Hershey's representative told the New York Times that the company has the rights to manufacture Cadbury chocolate in America using different recipes and that importing British chocolate is an infringement.
The New York Times broke down the major differences between both chocolates.
"Chocolate in Britain has a higher fat content; the first ingredient listed on a British Cadbury's Dairy Milk (plain milk chocolate) is milk," Schlossberg writes. "In an American-made Cadbury's bar, the first ingredient is sugar."
The American versions also contain preservatives.
Furious Cadbury fans have started the hashtag #boycotthershey.
#BoycottHershey Why should you @Hersheys dictate what chocolate we eat? British & Irish RT http://t.co/2pxgF6RY7R pic.twitter.com/uC211n8hV6
- Michele Rosborough (@micheleros) January 25, 2015
Andrew Baker at The Telegraph speculated that Hershey's is afraid of Cadbury chocolate.
"It will seem more likely to anyone who has ever tasted Hershey's own-brand products, and its approximations of Cadbury's, that they are instead preventing consumers from buying products which taste much better than Hershey's own," Baker writes.