The Swiss Federal Veterinary Office said the new case has been detected in a dead cow in a farm near St. Gallen, northeastern Switzerland.
Tests have shown it is a strain of atypical BSE (bovine spongiform encephalopathy) that, unlike typical BSE, is believed to rise spontaneously, rather than resulting from transmission through feed or the environment. Atypical BSE has been diagnosed in older cows across Europe.
The animal was born in September 2003, two and a half years after a total ban of animal feed came into force in Switzerland and the rest of Europe.
The latest case of mad cow disease in the country dates back to 2006, the office said in a statement.
Experts say the situation in Switzerland remains overall positive, but warn that isolated strains of BSE can still occur.
Since the first case was detected in 1990, Switzerland recorded a total of 464 cases of mad cow disease, the statement said.