In this study, the effect of montmorillonite (MMT) and compatibilizers content on the mechanical/thermal properties of low density polyethylene (LDPE) was studied. Maleated LDPE was compounded in a kneader with different MMT loadings. The maleic anhydride(MA)-grafted LDPE (LDPEgMA) nanocomposites were then molded by conventional and microcellular injection molding process. The effect of MMT and compatibilizers content on the mechanical/thermal properties was investigated. The results showed that LDPEgMA nanocomposites (up to 5 wt.% MMT loading) have better tensile strength and wear resistance than their neat counterparts, using either the conventional or microcellular injection molding process. In addition to the mechanical properties, the LDPEgMA nanocomposites also have better foaming property (i.e., cell size and cell density) than their neat counterparts. The thermal stability of the LDPE material is also improved by the addition of MMT.