A six parent modified half diallel of blackcurrants was planted in a randomised complete block design at Irwell, Canterbury, New Zealand. Variance components, heritability and breeding values were estimated for nine antioxidant traits from processed whole blackcurrant fruit harvested in 2004. Additive genetic effects were the largest with relatively small dominance and experimental design effects. Phenotypic and genetic correlations were moderately high (rp > 0.53, rg > 0.46) between all traits apart from correlations with relative antioxidant activity and bioavailability ratios and the correlation between delphinidin rutinoside and cyanidin-glucoside. Narrow-sense heritability estimates were moderate to high (0.46-0.80) except for the relative antioxidant activity and bioavailability ratios (0.28), indicating that phenotypic selection of parents may be successful. Implications are discussed for breeding blackcurrants with increased antioxidant levels.