Reactive melt blending of polyamide 6 (PA) and polysulfone (PSU) was carried out and the effect of the copolymer architecture on the pull-out of the copolymer in situ-formed during reactive blending was studied. To create various block and graft copolymers by reactive blending, three types of reactive PSU were prepared and used; maleic anhydride-grafted PSU, carboxylic-grafted PSU, and phathalic anhydride-terminated PSU. Polymer blend morphology was observed by transmission electron microscopy (TEM). The TEM results suggested that the block copolymers with linear chain structures are more easily pulled out to form micelles in the matrix than the graft copolymers having branch structure with trunk chains locating in the dispersed phase. Such graft copolymers stayed at the interface and played the role of emulsifiers. By contrast, the in situ-formed graft copolymers having trunk chains locating in the matrix were easily pulled out. The micelle formation via the pull-out of copolymers took place even in the rather symmetric block or graft copolymer system. Such interfacial behavior is against the current theories on polymer-polymer interface, which deal with the chain statistics under quiescent state; implying that the hydrodynamic contribution plays an important role of the pull-out.