The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated N‐cyclohexylhydroxy‐diazene‐1‐oxide, copper salt to derive a maximum concentration at the workplace (MAK value), considering all toxicity endpoints. Available unpublished study reports and publications are described in detail. Systemic target organs are liver and kidneys with a relatively high NOAEL. Due to its corrosivity to the eyes and release of copper in aqueous solutions, which may induce effects in the respiratory tract, the MAK value for copper is adopted, resulting in a MAK value of 0.05 mg/m3 N‐cyclohexylhydroxy‐diazene‐1‐oxide, copper salt for the respirable fraction. Like copper, it is classified in Peak Limitation Category II with a default excursion factor of 2 as no half‐life in blood is known. The NOAEL for developmental toxicity and maternal toxicity was 100 mg/kg body weight and day for rats and 10 mg/kg body weight and day for rabbits, corresponding to 140 and 23.3 mg/m3, respectively. Damage to the embryo or foetus is unlikely when the MAK value is observed and the substance is classified in Pregnancy Risk Group C. Calculations of dermal absorption based on in vitro studies show that dermal absorption would contribute substantially to the systemic toxicity. Therefore, N‐cyclohexylhydroxy‐diazene‐1‐oxide, copper salt has been designated with an “H”. N‐Cyclohexylhydroxy‐diazene‐1‐oxide, copper salt is not genotoxic or carcinogenic and not a contact sensitizer in humans and guinea pigs.