Ethylene-octene copolymer (EOC)/organically modified Montmorillonite (OMMT) nanocomposites were prepared by melt mixing method in an internal mixer. The nanocomposites were then dynamically cross-linked with 0.25, 0.5, 0.75 and 1 wt% dicumyl peroxide (DCP). The results of low angle X-ray diffraction and transmission electron microscopy (TEM) micrographs demonstrated that the OMMT platelets were mainly intercalated by EOC. According to our findings, a mechanism has been proposed for the separation of OMMT layers from each other upon cross-linking. Thermogravimetric analysis (TGA) showed that the OMMT incorporation enhanced the thermal degradation of EOC. A schematic diagram was also prepared to show the main steps of EOC and the nanocomposites degradation with temperature under N-2 and air atmospheres. Moreover, it was found from the rheological results that all of the cross-linked nanocomposites behaved as shear thinning fluids over the entire range of frequency. The molecular weight between cross-links (M-c) was estimated using James-Guth as well as Mooney-Rivlin theory. The results indicated that Mc decreased with increasing of the curing agent.