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Recent interest has focused on the role of reactive oxygen species (ROS) as universal constraints in life-history evolution. Empirical studies have examined the oxidative costs of reproduction for females, with little work conducted on males. The male germline is thought to be particularly susceptible to oxidative damage because the testes, and the sperm themselves, can be prolific producers of ROS. We tested the hypothesis that protection of the male germline from oxidative damage represents a cost of reproduction for males. We fed male crickets, Teleogryllus oceanicus, with one of two experimental diets in which we manipulated the availability of dietary antioxidants, and we induced variation in their expenditure on courtship effort by manipulating access to females. We measured the total antioxidant capacity, levels of ROS production and the amount of oxidative damage to proteins in both testis and thoracic muscle tissues. Dietary antioxidants contributed to positive oxidative balance in both tissue types. Although the testes had greater antioxidant defences than muscle tissue, they also produced considerably higher levels of ROS and sustained higher levels of oxidative damage. Courtship effort had no impact on any measure of oxidative balance. Our data confirm that the male germline is especially susceptible to oxidative stress and that dietary antioxidants can alleviate this oxidative cost of reproduction.