The graft copolymerization of undecylenic acid, oleic acid, and crotonic acid onto acrylonitrile-butadiene-styrene terpolymer (ABS) was initiated by benzoyl peroxide (BPO) in 1,2-dichloroethane solution, The infrared spectra confirmed that undecylenic acid, oleic acid, and crotonic acid were successfully grafted onto the ABS backbone. The grafting occurred at the butadiene region of the ABS. The grafting degree increased with increasing monomer concentration, but it decreased after monomer concentration, reaching 0.30 mol/L in undecylenic acid and oleic acid systems. The grafting degree increased rapidly with increasing initiator concentration, but slowed down at about 0.012 mol/L of initiator concentration. The grafting degree decreased considerably with increasing ABS concentration; however, the total amount of grafted monomer increased. Increasing reaction time and temperature led to an increase in grafting degree. The chain length of the monomer has a great influence on grafting, The grafting degree decreases with increasing the chain length due to a steric hindrance and monomer cage effect, which is in agreement with activation energy calculation, The overall activation energy of crotonic acid, undecylenic acid, and oleic acid systems are 118, 122, and 134 kJ/mol, respectively.