This is probably the first report on maleic anhydride (MA) grafted atactic polypropylene (aPP) acting as a typical compatibilizer for synthesis of poly(ethylene-co-octene) (POE) organically modified montmorillonite (OMMT) nanocomposites. The maximally grafted aPP (93.67% with 3 wt % MA) was used for compatibilization. OMMT concentrations were varied as 1, 3, and 5 wt % with respect to POE. Only moderate improvements in mechanical and rheological properties were recorded in both uncompatibilized (POE-OMMT) and compatibilized (POE-OMMT-1 wt % compatibilizer) nanocomposites due to predominant aggregation of OMMT layers. However, at higher compatibilizer content, e.g. 3 and 5 wt %, similar properties were hugely improved (92% rise in tensile strength, 55% rise in net elongation, etc.) due to partial delamination of OMMT galleries. Better processability including reduced die swell and flow activation energy and smoother extrudate profiles were also obtained as additional benefits at those compositions due to orientation of the delaminated OMMT layers in the flow direction.