The effects of molecular weight (M-w) of polystyrene (PS) latex particles on optical and electrical percolations of multi-walled carbon nanotube (MWCNT)-added nanocomposite films were reported. Three different latex particle solutions, each having different M-w, were first mixed with MWCNT dispersions at various mass fractions between 0 and 20 wt.% to prepare nanocomposites, and then the drop-casting method was employed to coat glass substrates by nanocomposite films. Surface resistivity, photon transmission and scanning electron microscopy measurements were performed on prepared films. As a result, the M-w of latex particles had no influence on both optical, wo and electrical percolation, phi(c) thresholds and the same threshold values were determined as 1.5 wt.%. Upon decreasing the latex M-w, a steady reduction from 3.99 to 2.28 was observed for the critical exponents of electrical percolation, beta(c) whereas almost similar critical exponents of optical percolation (averaged beta(o) approximate to 0.20) were found without any trend.