A method of preparing a flame retardant grafted polyolefin resin is provided. The method includes a step of reacting in an extrusion barrel a reactive polyolefin and a monomeric flame retardant agent to form the flame retardant grafted polyolefin resin. The reactive polyolefin has a functional group including a moiety selected from the group consisting of anhydrides, epoxies, carboxylic acids, ketones, and isocyanates. The monomeric flame retardant agent has an amine functional group. The method also includes a step of extruding the flame retardant grafted polyolefin resin. Also provided is a flame retardant grafted polyolefin resin that can be made according to the method. Further provided is a flame retardant cable that incorporates can incorporate the flame retardant grafted polyolefin resin.