Linear (EP)n multiblock copolymers, with n = 2, 4, 6, 8, 10, and 12, containing semicrystalline poly(ethylene) (E) and rubbery poly(ethylene-alt-propylene) (P) blocks were prepared by catalytic hydrogenation of poly(1,4-butadiene-b-1,4-isoprene)n block copolymers. These materials were investigated by small- and wide-angle X-ray scattering (SAXS and WAXS), transmission electron microscopy (TEM), and tensile mechanical testing. Microstructure was created during cooling in two ways: melt state ordering followed by E crystallization and crystallization-induced segregation from the disordered melt. Two categories of mechanical performance were identified. A relatively low true stress at break (σT,B < 85 MPa) always was correlated with crystallization-induced segregation. A high true stress at break (σT,B ≈ 270 MPa) was recorded when crystallization occurred within microphase-separated lamellae or when n ≥ 10 notwithstanding crystallization-induced segregation. These results are interpreted on the basis of the degree of coupling between E crystals, which depends on the mode of ordering. This model is supported by SAXS and WAXS data obtained from shear oriented (EP)2 triblock copolymer and differential scanning calorimetry results collected from all the multiblock copolymers.