The major aim of the present study was to investigate the influence of juglone (JU; 5-hydroxy-1,4-naphthoquinone) treatments on the expression level of Cat1, Cat2 and Cat3 genes, encoding the respective catalase isozymes in maize (Zea mays L.) and wheat (Triticum aestivum L.) seeds. In parallel, germination efficiency, catalase (CAT) activity and hydrogen peroxide (H2O2) content in juglone-exposed cereal seeds were assessed. Juglone applications significantly stimulated abundance of three target catalase transcripts as well as induced CAT activity and generation of H2O2 in both maize and wheat kernels. Furthermore, germination process of juglone-affected maize seeds was more severe suppressed than in case of wheat kernels. The role of juglone in triggering the oxidative stress as well as antioxidative responses in seeds of the studied model cereal species are discussed.