In this article, elastoplastic properties of polymeric nanocomposites embedded with carbon nanotubes (CNTs) are explored with emphasis on the meso-scale phenomena. To this end, a combination of finite element method and micromechanics is implemented. Accordingly, at first, considering the non-bonded nature of nanotube/polymer interactions, a multiscale finite element method is employed to replace the matrix, CNT, and polymer atoms neighboring it with a perfectly bonded equivalent nanofiller. Subsequently, nanocomposite stress-strain curves are extracted based on the mean field homogenization approach. Using this model, the effects of CNTs orientation and their agglomeration on the mechanical behavior of nanocomposite samples are thoroughly studied. Moreover, it is found that to have an efficient reinforcing effect, the CNT length should be greater than 10 nm. On the other hand, it can be concluded that there is an optimum value of this parameter (i.e. 300 nm) above which, there is no any extra stiffening effect. Furthermore, regarding the CNTs agglomeration, it is revealed that although, theoretical investigations show that increasing CNT volume fraction(VF) leads to an increase in the stiffness, occurring this phenomenon can have a deteriorative role in terms of influencing the mechanical behavior of these nanocomposites at higher VFs.