The zinc (Zn) is an important microelement for all living organisms but its deficiency or excess caused negative effect on metabolism. The aim of this study was to investigate the effect of Zn deficiency and excess on total catalase (CAT) activity and HvCAT2 gene expression, encoding one of the enzyme isoforms in barley leaves. It was shown, that deficiency and excess of Zn resulted in decrease in growth and biomass accumulation of barley seedlings. The Zn deficiency (0 µM) did not affect the MDA content in leaves, in contrast the Zn excess (1000 µM) caused increase in MDA level that is marker reaction of developing oxidative stress. Both Zn deficiency and excess resulted in significant increase in HvCAT2 transcripts accumulation in leaves of barley, on the day 7 of experiment. Under the Zn deficiency the mRNA of HvCAT2 decreased on day 14 while the CAT activity did not change which indicates to the normalization of redox balance of cells. However, Zn excess resulted in decline in CAT activity despite the high HvCAT2 transcripts amount and developing oxidative stress that can be an evidence of involvement of supplementary mechanisms of protection and/or reparation. In general, the results showed the participation of CAT and the HvCAT2 gene in the adaptation of barley plants to both Zn deficiency and an excess.