Poly(4-methyl-1-pentene) (PMP)/elastomer (ethylene-propylene-diene monomer (EPDM), polyolefin elastomer (POE), and styrene-butadiene-styrene (SBS)) blends with various mass fraction were prepared using a twin-screw extruder in the melt state. Mechanical properties, the fracture morphology, melting and crystallization behavior, and melt flow rate of PMP and PMP/elastomer blends were investigated by universal testing machine, differential scanning calorimeter, scanning electron microscopy, and melt flow indexer. The effect of elastomer and their content on the microstructure and properties of the PMP/elastomer blends were discussed. The results showed that EPDM, POE, and SBS all had good effect on PMP toughening. Therein, PMP/POE blends had the best comprehensive property, which was attributed to the comprehensive effects of phase morphology, molecular chains tangle, and the degree of crystallinity of PMP phase.