<p>A polymer matrix of polyolefin/clay nanocomposites with polypropylene/ethylene–octane copolymer (EOC) blend and Cloisite 15A as a nanofiller was fabricated and characterized. The nanocomposites were prepared with a fixed PP/EOC blend ratio, and different amounts of nanofiller, including 0, 1, 3, and 5% (by wt). The structural, morphological, rheological, and mechanical properties of the nanocomposites were evaluated by various tests. XRD results showed that with increasing the amount of nanofillers, the d-spacing of clay increased, while the size of clay galleries decreased. SEM images revealed that by incorporating nanofillers into the polymer blend, the size of dispersed phase decreased from 152 nm in the polymer blend to 123 nm in the nanocomposite with 5% (by wt) Cloisite. Rheometrics mechanical spectrometer&#xa0;(RMS) results disclosed that the complex viscosity, storage modulus, shear-thinning behavior, and relaxation time increased proportionally with the amount of nanofillers, and the nanocomposite with 5% (by wt) Cloisite had the highest solid-like behavior. Mechanical test confirmed that with increasing the amount of nanofillers, the tensile strength and elastic modulus increased, while the elongation-at-break and impact strength decreased. By adding 5% (by wt) Cloisite to the polymer blend, the tensile strength and modulus increased by 18 and 23%, and elongation-at-break and impact strength decreased by 74 and 17%, respectively.</p> Graphical abstract <p></p>