Oxidative stress results from increased production of free radicals and reactive oxygen species, and a decrease in antioxidant defense. This study was conducted to assess sexual dimorphism in serum biochemistry and oxidative status of West African dwarf lambs. Sixteen each of rams and ewes 8months old were randomly selected from a herd purchase from livestock market, Oyo. The average body weights of the lambs were 12.08±3.26 and 12.76kg ewes and rams, respectively. Fastened blood samples were collected from the sheep and assayed for serum biochemical, lipid peroxidation, total antioxidant activity, catalase and superoxide dismutase using standard procedures, data obtained were subjected to T-test. The result indicated that both sex had similar serum biochemical indices except total protein. Ewes had significantly higher serum protein than ram. Rams had apparently higher total antioxidant activity and significantly higher serum catalase activity than ewes, while serum lipid peroxidation and superoxide dismutase were statistically similar in both sexes. This indicates that rams have better antioxidant activity than ewes. During oxidative stress prone conditions and environment, measures to boost antioxidant activity of ewes should be emphasized.