Five sweet orange (Citrus sinensis Osbeck) varieties cultivated in Huelva (Spain) and picked at two seasons during two consecutive years, were characterized for their antioxidant activity (free radicals scavenging activity, reducing power and lipid peroxidation inhibition) and vitamin content (vitamin E and vitamin C). The effects induced by sweet orange variety and stage of maturity were comprehensively compared by applying 2-way ANOVA and linear discriminant analysis. The results indicated higher differences in antioxidant activity and vitamin contents in response to the effect of the harvesting season, when compared to the effect of sweet orange variety. Nevertheless, the results observed in 2012 showed less marked differences among the assayed sweet orange varieties. Either way, it might be concluded that oranges sampled in January show the highest antioxidant activity and vitamin contents. Furthermore, concerning the properties evaluated in this work, all sweet orange varieties represent good alternatives, except for Rhode Summer, which would not be the preferable choice as a target to enhance sweet orange overall characteristics.