The study is aimed at assessing the effect of biofertilizers, based on plant growth promoting rhizobacteria (PGPR), on biomass and the content of low molecular weight antioxidants in Brassica oleracea L. (cultivar ‘Express’ F1) within copper biofortification. A strain of metallotolerant growth promoting rhizobacteria ( Bacillus altitudinis , TF16a) was isolated from the rhizosphere soil of Tussilago farfara L. in the vicinity of the copper smelting plant, and a liquid bacterial culture (108 CFU/ml) was used to create the biofertilizer. Biochar made of birch wood was chosen as the carrier material for PGPR. The plants were grown in plastic pots in a growing chamber for 30 days: photoperiod - 14 : 10 (day : night), illumination - 150 ±20 mcm/m2, temperature - 23 ±2 oC. The experiment included 4 variants in 2 independent repetitions: a control peat substrate added by 5 % biochar by volume; a substrate added by 5% biofertilizer based on PGPR and biochar; a substrate added by 100 mg/kg of copper; a substrate added by 5 % biofertilizer and 100 mg/kg of copper. The soil was treated with copper sulfate solution (sulfate form). The study has shown that the bacterial biofertilizer prevented excessive accumulation of copper ions in the organs of B. oleracea and stabilized them in the underground biomass. The biofertilizer and copper jointly introduced into the soil had a positive effect on the aboveground and underground biomass of B. oleracea , increasing it by an average of 23 %. Within the biofertilizer, accumulation of such low molecular weight antioxidants as carotenoids, free proline and soluble phenolic compounds, including flavonoids in B. oleracea leaves increased significantly (by an average of 33 %)., which is likely to increase plants resistance and improve their biological value. It is concluded that biofortification of cabbage plants with copper, along with the biofertilizer, increased the antioxidant activity in B. oleracea .