Polystyrene-b-n-butyl methacrylate, PS-b-PBMA, star block copolymers having different strengths of segregation are investigated with respect to their deformation behavior. Disordered block copolymers are deformed by craze mechanism corresponding to the glassy homopolymer comprising the block copolymer. At the order-disorder transition (ODT), a transition from crazing to shear deformation is observed. Closer investigations reveal the shear yielding of lamellar grains with different orientations. This observation is clearly in contrast to deformation behavior of diblock copolymers that show a cavitation mechanism. Shear deformation in microphase-separated star block copolymers demonstrates the influence of molecular architecture on deformation behavior. Tensile properties of star block copolymers are compared with di- and triblock copolymers. It is found that star block architecture results in an increase of strain at break compared to di- and triblock copolymers. The yield stress is lower compared to triblock copolymers, indicating the influence of architecture and entanglements.