This paper established the procedure to fabricate MWNT/PMMA nanocomposite by using both the injection molding and film casting processes. The combined fabrication process could remove demerits while maintaining the merits of each process. Tensile strength of the MWNT/PMMA nanocomposite increased more than 15% and tensile stiffness also increased about 17.5%, compared to the pure PMMA. It was confirmed that this combined fabrication process efficiently dispersed MWNTs in the PMMA matrix, and also maintained the well-dispersed state more effectively. SEM images of the fractural surface show that the degree of dispersion was improved. In addition, a surfactant was used to disperse MWNTs more efficiently, and its effect on mechanical properties was also investigated.