The combine effect of nanotube pre-treatment method (freeze drying (FD) vs. oven drying (OD) ), density, powder size and length of fourteen multi-walled carbon nanotubes (MWCNTs) on the dispersion and further on the percolation and mechanical behavior of polycarbonate (PC)/MWCNTs nanocomposites was investigated. Nanocomposites were melt mixed in a twin-screw micro-compounder at concentrations of 0.1-3.0 wt% MWCNTs. Tensile strength was independent of MWCNT concentration while the Young’s modulus slightly increases and strain at break appreciable decreases when compare with pure PC. Scanning electron microscopy (SEM) and Bright field light microscopy (LM) micrographs were collected to evaluate the effect of the density, length, powder size and pre-treatment method at sub-micron and macro scale, respectively. Dispersion and CNT waviness played a bigger role than aspect ratio on the electrical properties of PC/MWCNTs composites. Additionally, a mechanism that explains the electrical properties reported in this paper and in the key literature in the topic of freeze drying vs oven drying was developed.