In this contribution, random copolymers of p(styrene-co-acrylonitrile) via initiators for continuous activator regeneration (ICAR) in atom transfer radical polymerization (ATRP) (ICAR ATRP) of styrene and acrylonitrile (SAN) were synthesized at 90°C in low molecular weight polyethylene glycol (PEG-400) using CCl4 as initiator, FeCl3·6H2O as catalyst, succinic acid as ligand and thermal radical initiator azobisisobutyronitrile (AIBN) as thermal free radical initiator. In this system, well-defined copolymer of SAN was achieved. The kinetics results showed that the copolymerization rate obeyed first-order kinetics model with respect to the monomer concentration, and a linear increase of the molecular weights with the increasing of monomer conversion with narrow molecular weight distribution was observed in the range of 1.1–1.5. The conversion decreased with increasing the amount of FeCl3·6H2O and increased with increasing the molar ratio of [St]0/[AN]0/[CCl4]0 and temperature. AIBN has a profound effect on the polymerization. The activation energy was 55.67 kJ mol−1. The living character of copolymerization was confirmed by chain extension experiment. The resultant random copolymer was characterized by 1H-NMR and GPC. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40135.