The disease, which does not affect humans, was found in two dead wild boars that may have crossed the border into the Zlín region.
Special monitoring of the wild boar population has been introduced, Agriculture Ministry said on Tuesday.
No pig farm was affected so far.
A 10-km sanitary perimeter has been established including a farm with around 5,000 pigs that are being inspected.
If domesticated pigs catch the disease they have to be put down and cordons placed around the farms in question.
According to the World Organisation for Animal Health (OiE), there is no published treatment or vaccination for ASF.