It has been investigated the in vitro antioxidant properties of ethanol extracts of the contained-allantoin plants in this study. Contained-allantoined plant samples Plantago lanceolata, Plantago major, Robinia pseudoacacia, Platanus orientalis and Aesculus hippocastanum were tested at different concentrations. The antioxidant activities of plant samples were analysed by 1,1- diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method, cupric reducing antioxidant capacity (CUPRAC), reducing power assay and β-carotene bleaching method. Plantago major plant showed the highest antioxidant capacity compared to other plant extracts in results of the in vitro assays including 1,1- diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method with 90.25 %, cupric reducing antioxidant capacity (CUPRAC) with 1.789 %, reducing power assay (FRAP) with 1.321 % and β-carotene bleaching method with 78.01 % in 1 mg/mL. The lowest antioxidant activity was determined in Robinia pseudoacacia plant. In conclusion, allantoin shows antioxidant properties and it has positive the effect on total antioxidant capacity.