This highly soluble turquoise coloured salt is a common source of the Ni2+ ion for electroplating.

Columns used in polyhistidine-tagging, useful in biochemistry and molecular biology, are regenerated with nickel sulfate.

The second hexahydrate is known as nickelhexahydrite (Ni,Mg,Fe)SO4·6H2O, which is the monoclinic dimorph of retgersite.

[8] Nickel sulfate is classified as a human carcinogen[9][10] based on increased respiratory cancer risks observed in epidemiological studies of sulfidic ore refinery workers.

[11] In a 2-year inhalation study in F344 rats and B6C3F1 mice, there was no evidence of carcinogenic activity, although increased lung inflammations and bronchial lymph node hyperplasia were observed.

[12] These results strongly suggest that there is a threshold for the carcinogenicity of nickel sulfate via inhalation.

In a 2-year study with daily oral administration of nickel sulfate hexahydrate to F344 rats, no evidence for increased carcinogenic activity was observed.