A literature review is conducted on performed investigations for characterizing Young's modulus of nanoclay platelet as the reinforcing agent of nanoclay/polymer nanocomposites from both experimental and theoretical aspects. The observed discrepancies in the reported results are discussed accordingly. All available investigations for predicting mechanical properties of nanoclay reinforced polymers are also reviewed. The employed methods in ongoing studies are categorized into three groups as atomistic, continuum and multiscale modeling techniques. Those challenging issues which are still in need of more accurate understanding and discussion are identified and outlined through a gap analysis on current investigations. The introduced shortcomings can be considered as prospective research areas for the future studies in the field of estimating mechanical properties of nanoclay based composites. POLYM. COMPOS., 40:431–445, 2019. © 2018 Society of Plastics Engineers