The effects of multi-walled carbon nanotubes (MWCNTs) with different functional groups on the properties of the polycarbonate (PC)/poly (lactic acid) (PLA) was investigated. Non-functionalized (MWCNT), hydroxyl-functionalized (MWCNT-OH), carboxyl-functionalized (MWCNT-COOH), and polycarbonate-grafted multi-walled carbon nanotube (PC-g-MWCNT) were selected as nano-additives for PC/PLA. PC-g-MWCNT were prepared by reacting between the hydroxyl groups on MWCNT-OH and the carbonyl groups in PC by the reactive extrusion. Fourier transformed infrared spectroscopy (FTIR) analysis was performed to support the functionalization process and determined the chemical structure of the modified nanotube. MWCNTs were compounded with PC/PLA in a twin-screw micro compounder and moulded with the laboratory-scale injection moulding machine. Nano-additives was added to the polymer matrix at 3-5 wt.% loading levels. Characterization of the prepared samples was realized by the thermal, mechanical, electrical conductivity, and morphological analysis. As a result of FTIR analysis, nanotubes were seen to bind successfully to the PC. The best effect at onset decomposition temperatures was achieved by increasing about 39.8 degrees C with the addition of 5 wt.% MWCNT-OH to the PC/PLA. The highest elongation at break, tensile strength, and modulus was obtained for nanocomposites containing MWCNT-COOH. The selective localization of PC-g-MWCNT in the matrix provided the highest electrical conductivity in 5 wt.% PC-g-MWCNT added nanocomposite.