Well-defined epoxy functionalized four-armed star diblock copolymers were synthesized by atom transfer radical polymerization (ATRP) using the “core-first” approach. In accordance with this synthetic methodology, in a first step, bromine-terminated four-armed star homopolymers of styrene (S) and methyl methacrylate (MMA) were prepared. Then, in a second step, the S[PS-Br] 4 and S[PMMA-Br] 4 samples were employed as macroinitiators in the ATRP of an oxirane functionalized monomer, like glycidyl methacrylate (GMA). These copolymerization reactions were carried out in benzonitrile solution, at relative-low polymerization temperature, 50 °C, and using copper chloride with N, N, N′, Nʺ, Nʺ-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. Linear first-order kinetics with respect to the [GMA] 0 were observed, and the analyses of the copolymers obtained by means of size exclusion chromatography (SEC) and 1H nuclear magnetic resonance spectroscopy ( 1H NMR) demonstrated the high degree of control achieved in the copolymerizations. Moreover, their crosslinkable capacity was studied with a linear diamine by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), indicating their clear potential for epoxy resins technologies.