Nanocomposites present interesting mechanical properties owing to the high surface-area-to-volume ratio of the dispersed reinforcement. The vibration weldability of these new composites has not yet been reported in the literature. This research examines the effect of the vibration-welding parameters of weld pressure and target meltdown on the strength of butt welds made from two polypropylene-based nanocomposites. The nanocomposites were made by melt-compounding two levels of organoclay with polypropylene. The results of unreinforced polypropylene are shown for reference. All welded assemblies were assessed by tensile testing. The results show that 3-6% of organoclay reinforcement causes a significant decrease in weld strength.