Heat stress (HT) is a factor seriously affecting the semen quality and antioxidant status of roosters. This study was designed to evaluate the effect of chive bulb extract (CBE), as a natural antioxidant, on roosters exposed to heat stress (HT). Twenty-four 3F-Viet roosters were randomly divided into 3 treatments (CBE was added to drinking water at 3 doses: 0, 1 or 2 ml/l) with 4 replicates to determine the effect of CBE on semen characteristics and some blood biochemical parameters of roosters in the hot season. Treatments with CBE at concentrations of 1% or higher significantly improved semen characteristics, including semen volume, sperm concentration, and motility (p > 0.05), while significantly reducing sperm mortality and abnormalities (p < 0.05) compared to the control. In addition, the antioxidant malondialdehyde was significantly reduced (p<0.05), whereas TAC and serum levels of LH, FSH and testosterone significantly increased (p<0.05) in the treatment supplemented with 2% CBE. It can be concluded that CBE possessed fertility-promoting properties in roosters due to its antioxidant properties and increased reproductive hormone activity.