Livestock development particularly in dairy cows have been hampered by low production including milk and growth rate due to many pathogens including Neospora caninum. N. caninum, an obligate intracellular protozoan parasite, is the causative agent of neosporosis recognized as a major cause of bovine abortion around the world and known to have a detrimental effect on bovine pregnancy and on milk production. Currently, there is no effective method for control of neosporosis since there is less information regarding current status of infections. The objective of this study was to investigate the seroprevalence of neosporosis in dairy cows of the Northeast of Thailand. In 2007, the sera of 445 cows of 55 small holder farms from the top three highest consensuses of dairy farms in the Northeast provinces such as Khon Kaen, Udorn Thani, and Sakon Nakhon were collected. Antibodies to N. caninum were assayed by c-ELISA (VMRD, USA) and 52 (11.7 %) found seropositive. Cows with age more than 5 years had the highest seroprevalence (13 %) compared to age between of 1 and 5 years (11.5%) and less than age of 1 year (6.1%). Khon Kaen had the highest endemic area for N. caninum infections in dairy cows (12.9%). A total of dairy farm infections was 58.2% (32/55). The high incidence of N. caninum infections in cows indicated the risk of Thai farmers to realize and understand the problem of dairy cow’s infertility in their farms. This result would be beneficial for controlling strategy of neosporosis of food animals in Thailand.