AbstractThis experiment was conducted to evaluate the effects of dietary Securigera securidaca seed powder on growth performance, haematological parameters, cardiac indices, electrocardiographic parameters and expression of catalase (CAT), endothelin 1 (ET‐1) and inducible nitric oxide synthase (iNOS) genes in the lung in the broilers reared at high altitude (2,100 m above sea level). A total number of 200‐day‐old male broilers (Ross 308) were randomly assigned to five treatments including different levels of S. securidaca 0, 1, 2, 3 and 4 g/kg in a 42‐day trial. The results of this experiment showed that the dietary inclusion of S. securidaca powder improvement in feed conversion ratio (p < 0.05). The dietary utilization of 2–4 g/kg S. securidaca significantly increased concentrations of nitric oxide (NO), although significantly lower serum concentrations of malondialdehyde (MDA) and significantly decrease T, R, S electrocardiogram waves compared with control group. Also, the dietary inclusion of 2–4 g/kg S. securidaca prevented right ventricular hypertrophy and increased the expression of iNOS and CAT genes in lung tissue of broilers. On the other hand, S. securidaca significantly suppressed the expression of ET‐1 in lung tissue. Generally, the results of this study showed that the use of 3 g/kg of medicinal plant S. securidaca can be beneficial in prevention of pulmonary hypertension syndrome (PHS) in broiler chickens reared at high altitudes.