Iron and zinc are necessary nutrients whose homeostasis is tightly controlled by members of the ferric uptake regulator ( FUR ) superfamily in the cyanobacterium A nabaena sp. PCC 7120. Although the link between iron metabolism and oxidative stress management is well documented, little is known about the connection between zinc homeostasis and the oxidative stress response in cyanobacteria. Zinc homeostasis in A nabaena is controlled by Z ur, also named FurB . When overexpressed in E scherichia coli , Z ur ( FurB ) improved cell survival during oxidative stress. In order to investigate the possible correlation between Z ur and the oxidative stress response in A nabaena , zur deletion and zur ‐overexpressing strains have been constructed, and the consequences of Z ur imbalance evaluated. The lack of Z ur increased sensitivity to hydrogen peroxide ( H ₂ O ₂ ), whereas an excess of Z ur enhanced oxidative stress resistance. Both mutants displayed pleiotropic phenotypes, including alterations on the filament surfaces observable by scanning electron microscopy, reduced content of endogenous H ₂ O ₂ and altered expression of sodA , catalases and several peroxiredoxins. Transcriptional and biochemical analyses unveiled that the appropriate level of Z ur is required for proper control of the oxidative stress response and allowed us to identify major antioxidant enzymes as novel members of the Z ur regulon.