The grafting of acyl chloride-capped polymers onto carbon black by the reaction of the acyl chloride group with the phenolic hydroxyl group on the surface was investigated. Acyl chloride-capped polymers were prepared by the reaction of functional polymers having terminal hydroxyl groups, such as poly(propylene glycol) (PPG), poly(ethylene glycol) (PEG), and silicone diol (SDO), with adipoyl dichloride or isophthaloyl dichloride. When acyl chloride-capped PPG (PPG-COCL) ([Mbar]n= 2.4 × 103) was reacted with carbon black, PPG was grafted onto the surface: the percentage of grafting reached to 27.7%. on the contrary, the reaction of PPG-COC1 with carbon black treated with diazomethane was scarcely observed. the PPG grafted onto carbon black was largely removed by hydrolysis with a dilute methanol solution of KOH. Based on these results, it was concluded that PPG grafted onto the surface with ester bonds. the percentage of grafting increased with an increase in the molecular weight of PPG-COC1. in addition, it was found that carbon black containing amino and imidazoline groups has high reactivity with PPG-COC1 and gives PPG-grafted carbon black with a high percentage of grafting. PPG-grafted carbon black produced a stable colloidal dispersion in organic solvents.