Poly(n-butyl acrylate)-graft-branched polyethylene was successfully prepared by the combination of two living polymerization techniques. First, a branched polyethylene macromonomer with a methacrylate-functionalized end group was prepared by Pd-mediated living olefin polymerization. The macromonomer was then copolymerized with n-butyl acrylate by atom transfer radical polymerization. Gel permeation chromatography traces of the graft copolymers showed narrow molecular weight distributions indicative of a controlled reaction. At low macromonomer concentrations corresponding to low viscosities, the reactivity ratios of the macromonomer to n-butyl acrylate were similar to those for methyl methacrylate to n-butyl acrylate. However, the increased viscosity of the reaction solution resulting from increased macromonomer concentrations caused a lowering of the apparent reactivity ratio of the macromonomer to n-butyl acrylate, indicating an incompatibility between nonpolar polyethylene segments and a polar poly(n-butyl acrylate) backbone. The incompatibility was more pronounced in the solid state, exhibiting cylindrical nanoscale morphology as a result of microphase separation, as observed by atomic force microscopy.