Foot-and-mouth disease (FMD) is endemic in Iran. It is essential to timely evaluate the current disease control programme in Iran. Here, we report the frequency of FMD virus (FMDV) carrier state in cattle slaughtered in Mashhad abattoir, Mashhad, Khorasan Razavi, north–east of Iran, which contains long common borders with Afghanistan and Turkmenistan. Soft palate samples were collected immediately after slaughter for the detection of FMDV by RT-PCR. The results show that 37.7% of cattle (96 of 255) were carriers of the virus. Among positive samples (96), 58 (60.4%) belonged to serotype O. No evidence was detected for the presence of Asia 1 and A serotypes. Nucleotide sequencing and phylogenic dendogram showed close similarity and common lineage between our samples and viruses isolated in Pakistan. With an approximate more than 80% of cattle population vaccination coverage such a high rate of carrier state may show an extensive FMDV exposure. Therefore, limiting control programmes to timely prophylactic vaccination may be insufficient. This is also true when meat market instabilities act as a temptation to import livestock, legally or illegally, through the eastern frontiers. It is recommended to change the current prophylactic vaccination strategy to a well-developed regional control programme, with close monitoring of animal movement through eastern frontiers, supported by government commitment and educational programmes. Timely estimation of the frequency of carrier state both in cattle and small ruminants is also advocated as a gauge to monitor the virus status in the region.