In this study, microspherical poly(methyl methacrylate)/multi-walled carbon nanotube (PMMA/ MWCNT) composites were directly prepared by in situ dispersion polymerization using poly (N-vinylpyrrolidone) in methanol media. PMMA/MWCNT microspheres having a diameter of 2.6 approximately 3.9 microm and a molecular weight of 58,000 approximately 65,000 g/mol with a 15.7 approximately 19.5% coefficient of variation (Cv) were synthesized. The morphology of the synthesized composite was investigated using scanning electron microscopy and transmission electron microscopy. The experimental results demonstrated that MWCNTs are well dispersed and embedded in the final PMMA/MWCNT microspheres. The prepared PMMA/MWCNT microspheres were investigated in terms of their capacity to serve as an electrorheological (ER) materials.