A serological survey detected antibodies against Babesia ovis in mouflon sheep (Ovis musimon) from two different reserves located in Catalonia in northeastern Spain. An indirect fluorescent antibody test (IFAT) was developed using a B. ovis isolate of ovine origin as the antigen. Of 50 sera tested, six (12%) showed titres between 1:160 and 1:640 and were considered positive. These results indicate that exposure of mouflon to Babesia ovis is common in this region.