An electrostatic inkjet ink composition including: a non-aqueous solvent having a dielectric constant of from 1.5 to 20 and a surface tension at 25.degree. C. of from 15 to 60 mN/m; a color material that is insoluble in the non-aqueous solvent; and a charge control agent that is soluble in the non-aqueous solvent, wherein the charge control agent contains a half-aside maleic acid copolymer containing repeating units represented by the formulae (Ia) and (Ib) as defined herein.