Nickel(II) nitrite is an inorganic compound with the chemical formula Ni(NO2)2.

[4] The aqueous complex Ni(NO2)2(H2O)4 forms when an alkali metal nitrite is added to a nickel salt solution: The complex is a much more intense emerald green colour than the Ni(H2O)62+ ion.

Brooker claims that intense light photocatalyses the destruction of the ionic nitro complexes, leaving only Ni(NO2)2(H2O)4.

[4] Nickel nitrite slowly decomposes slightly in aqueous solution due to disproportionation:[4] In the presence of additional ligands, nickel nitrite can change colors substantially.

These color changes may arise from the new molecular orbitals, or linkage isomerism, in which the nitro ligands rearrange to a nitrito (-ONO) complex.