A charge control agent comprises a monoazo metals-compound including a monoazo compound represented by the following formula [I]: ##STR00001## and metals of a metallic element or a metalloid coordinating to the monoazo compound. A toner for developing an electrostatic image comprises: the charge control agent including the monoazo compound and metals of the metallic element or the metalloid coordinating to the monoazo compound, a resin for the toner and a colorant.