Abstract:  Seventeen‐day‐old piglets in a small holding farm in southern Thailand manifested signs of convulsion, fever, and death. The morbidity and mortality rate were approximately 26.09% (6/23) and 4.35% (1/23), respectively. Impression smear from lungs demonstrated tachyzoite stage of Toxoplasma gondii. Histopathological investigation revealed interstitial pneumonia. Further investigation, blood collection, educating the farmer, and prescribed affected herd with sulfa‐trimethoprim were performed soon after Toxoplasma infection was demonstrated. A serological detection of T. gondii infection among affected herds using latex agglutination test was conducted on 14 serum samples. The overall seroprevalence was 71.43% (10/14). The titers were 1:64 in 3 pigs (21.43%), 1:128 in 4 (28.57%), 1:256 in 2 (14.29%), and 1:512 in 1 (7.14%). A cat in this farm showed antibody titer 1:32 while a dog was seronegative. Data derived from this case indicated two possible routes of transmission: transplacental infection and ingested food or water contaminated with oocysts shed by cat in this farm. However, rodents can not exclude as a role of toxoplasmosis transmission. Serological monitoring at slaughter houses combine with good sanitary practices, rodent and cat control in the farm are important measures to prevent toxoplasma infection and improve human health in the future.