This article reports the synthesis of novel hydrophilic end-branched poly(ethylene glycol)s, in aqueous media by atom transfer radical polymerization (ATRP). Poly(ethylene glycol)s with molecular weights 10,000 and 16,000 were end-functionalized and used as bifunctional initiators for the polymerization of a poly(ethylene glycol) macromonomer with a molecular weight of 2,000 (PEGMA), either by aqueous ATRP or in a water/methanol (1/1 V/V) mixture. For both macroinitiators a DP of 10 was the target, giving an average of 5 branches in each end. The rates of polymerization were of the same order of magnitude when the polymerizations were initiated by either of the two macroinitiators in water/methanol (1/1 V/V). When a bifunctional oligo(ethylene glycol) initiator (M-n = 600) was used to study the polymerization of PEGMA in water/methanol a reduction in the rate of polymerization was observed indicating an influence of the molecular weight of the initiator on the rate of polymerization.