The citrate-assisted growth of nickel hexacyanoferrate (NiHCF) nanocubes was investigated. Control over the complexation of Ni2+ ions with citrate at different temperatures enabled fine tuning of the nanocrystal (NC) dimensions and their self-assembly into mesocrystals. Our results introduce new concepts towards the synthesis of NiHCF NCs, potentially applicable to other members of the Prussian blue analogues family.