The present study investigated the seroprevalence of porcine reproductive and respiratory syndrome virus, Aujeszky's disease virus (ADV), and porcine parvovirus (PPV) in replacement gilts from selected five swine herds in Thailand. The study consisted of three parts. First, a retrospective data analysis on the seroprevalence of porcine reproductive and respiratory syndrome virus (PRRSV) and ADV glycoprotein I (gI) in gilts, sows, boars, nursery, and fattening pigs in five herds (n = 7,030). Second, a cross-sectional study on seroprevalence of PRRSV, ADV, and PPV (n = 200) in replacement gilts. Last, the seroprevalence of PRRSV, ADV, and PPV in gilts culled due to reproductive failure (n = 166). Across the herds, the seroprevalence of PRRSV and ADV was 79.3% and 5.3%, respectively. The cross-sectional study revealed that 87.5%, 4.0%, and 99.0% of the replacement gilts were infected with PRRSV, ADV, and PPV, respectively. In the gilts culled due to reproductive failure, the seroprevalence of PRRSV, ADV, and PPV was 73.5%, 28.3%, and 86.0%, respectively. Of these culled gilts, 75.5% had been infected with at least two viruses and 18.9% had been infected with all three viruses. It could be concluded that most of the replacement gilts were exposed to PRRSV (84%), PPV (97%), and ADV (4%) before entering the breeding house. PPV was an enzootic disease among the selected herds. The prevalence of ADV was higher in gilts culled due to reproductive disturbance than in the healthy gilts.