Biodegradable stereocomplex-type poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA)/multiwalled carbon nanotubes (MWCNTs) nanocomposites are prepared via simple melt blending method at PDLA loadings from 5 to 20 wt %. Formation of the stereocomplex crystals in the nanocomposites is confirmed by the phase transition in the differential scanning calorimetric profiles. Field emission scanning electron microscopy observation indicates that MWCNTs are nicely dispersed in the PLLA/PDLA/MWCNTs ternary blends with 20 wt % PDLA loading due to the increased shear stress in the melt-compounding with presence of PDLA. The overall crystallization rates are faster in the PLLA/PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite; however, the crystallization mechanism and crystal structure of these nanocomposites remain unchanged despite the presence of PDLA. The storage modulus above glass transition temperature has been apparently improved in the PLLA/PDLA/MWCNTs nanocomposites with respect to PLLA/MWCNTs nanocomposite. It is interesting to find that the hydrolytic degradation rates have been enhanced obviously in the PLLA/PDLA/MWCNTs nanocomposites than in PLLA/MWCNTs nanocomposite, which may be of great use and importance for the wider practical application of PLLA/MWCNTs nanocomposites. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3919-3929, 2013