Polymeric carbon nanotube composites constitute one of the most promising alternatives to conventional filled polymers. The dispersion of nanometer-sized carbon nanotubes in a polymer matrix markedly improves its physical properties. This approach can also be applied to biodegradable synthetic aliphatic polyesters such as poly(L-lactic acid) (PLLA), which has been receiving an increasing amount of attention due to environmental concerns. In this study, the mechanical properties of PLLA were enhanced by the incorporation of a small amount of carbon nanotubes (0.8 wt%) in the solution state, which could make this material a good competitor for commodity materials such as general purpose plastics, while allowing it to retain its biodegradability. In order to obtain a homogeneous dispersion of the carbon nanotubes in the matrix, oxygen-containing groups were introduced on the surface of the MWNTs. The good dispersion of the nanotubes in the PLLA matrix observed by scanning electron microscopy was attributed to the fact that the PLLA was compatible with the functionalized MWNTs during the compounding process. The electrical conductivity of the composites was also investigated.