The interfacial slip of the immiscible isotactic polypropylene/polystyrene (PS) blends with different morphologies was studied. The morphologies were obtained by choosing different PS contents (7, 21, and 55 vol%) and different processing methods (multilayered co-extrusion and conventional blending). The interfacial slip was obviously found in the multilayered morphology and the co-continuous morphology, but did not occur in the sea-island morphology. Besides, it was observed that the slip velocity of the multilayered system was higher than that of the conventional blends with co-continuous morphology and could be promoted with the increase of layer numbers. However, the interfacial slip in the multilayered system would be suppressed by the layer deformation and breaking during the test, when the thickness of layers was thin enough. The effect of composition on the interfacial slip velocity was also discussed in the multilayered composites.