Carbon nanotubes (CNTs), with their high aspect ratio and exceptionally high mechanical properties, are excellent fillers for composite reinforcement if they are uniformly dispersed without aggregation. Combining the latex compounding and self-assembly techniques, we prepared a novel natural rubber (NR)/multiwalled carbon nanotube (MWCNT) composite. Before self-assembly, the MWCNTs were treated with mixed acid to ensure that the MWCNTs were negatively charged under an alkaline environment. The structure of the MWCNTs was tested with Fourier transform infrared spectroscopy. The properties of composites with different MWCNT loadings were characterized with transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and tensile testing. The results indicate that the MWCNTs were homogeneously distributed throughout the NR matrix as single tubes and had good interfacial adhesion with the NR phase when the MWCNT loading was less than 3 wt %. In particular, the addition of the MWCNT led to a remarkable reinforcement in the tensile strength, with a peak value of 31.4 MPa for an MWCNT content of 2 wt %, compared to the pure prevulcanized NR (tensile strength = 21.9 MPa). The nanocomposites reinforced with MWCNTs should have wide applications because of the notable improvement in these important properties. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012