Heat stress (HS) is the main challenge facing livestock health. The present work aimed to study the oxidative stress status in the blood of desert Barki lambs during the hot dry season in El-Kharga oasis in the western Egyptian desert. Twenty-four male Barki lambs (4-5 months) were included in this study. Twelve of them were selected during July (hot dry, HS group) and the remaining 12 animals were selected during December (thermoneutral, TN-group) as controls. Temperature humidity index (THI) registered 65.4 (satisfactory) in winter and 89.6 (risky HS) in summer. Compared to controls, increased rectal temperature (P < 0.001) and respiration rate (P < 0.001) were detected in the HS group.  Red blood cells count (P < 0.001), packed cell volume (P < 0.01) and hemoglobin concentration (P < 0.001) were reduced in HS group. Increased total peroxides (TPx, P < 0.05), the free radical superoxide anion (P < 0.05) and decreased total antioxidant capacity (TAC, P < 0.05) were shown in plasma of the HS group. Malondialdehyde concentration as an indicator of lipid peroxidation was increased (P < 0.05) but superoxide dismutase activity was decreased (P < 0.05) in the erythrocyte of the HS group. Oxidative stress index (OSI, TPx/TAC ratio) increased (P < 0.05) in HS group. In conclusion, HS is associated with oxidative stress and corpuscular redox imbalance in lambs under tropical conditions.