Background: Ascites or pulmonary hypertension syndrome (PHS) is one of the significant problems in the poultry industry. Therefore, various studies have been conducted on its contributing factors. Objectives: This study aimed to investigate the role of vitamin E in reducing the mRNA levels of caspase-1 (CASP1), caspase-2 (CASP2), and caspase-3 (CASP3) genes involved in the apoptosis pathway. Methods: Ninety fast-growing 1-day-old chickens (Ross 308) were randomly assigned to three equal groups, including sham (basal diet), control (basal diet+1.5 mg/kg of triiodothyronine [T3]), and treatment group (basal diet+400 mg/kg of vitamin E+1.5 mg/kg of T3). To induce ascites, 1.5 mg/kg of T3 was added to basal diet from the seventh day to the end of the experiment. On the 21st and 49th days after rearing, 15 chicks from each group were randomly selected. The right ventricle/total ventricle weight ratio (RV/TV) and the expression levels of CASP1, CASP2, and CASP3 genes in the lung and right ventricle of all three groups of broiler chickens were measured and compared. Results: Although there was no significant difference between the three groups in terms of the RV/TV ratio on day 21 post-reared (P≥0.05), a significant decrease was detected in the vitamin E-receiving group compared to the control group with respect to the RV/TV ratio on day 49 post-reared (P<0.05). Also, vitamin E reduced the relative expression of CASP1, CASP2, and CASP3 at 49 days of age in the lung and heart tissues of broiler chickens with ascites (P<0.05). Conclusion: Based on the results of this study, it seems that vitamin E can reduce some apoptosis genes (CASP1, CASP2, and CASP3) associated with pulmonary hypertension in broilers.