Lignin-decorated thin multi-walled carbon nanotubes (t-MWNTs) were prepared to obtain mechanically strong poly(vinyl alcohol) (PVA) nanofibers (NFs) with high antimicrobial properties. The t-MWNTs were well-dispersed in the aqueous lignin solution owing to their good interaction with lignin molecules, resulting in decoration of the lignin molecules on the surface of the t-MWNTs. The lignin-decorated t-MWNT/PVA NF webs were prepared by electrospinning lignin/t-MWNT/PVA solutions containing 1 wt% t-MWNTs. They displayed enhanced mechanical properties in terms of breaking stress and modulus, compared to lignin/PVA nanofibers. Superior antimicrobial activity was also exhibited by the lignin/t-MWNTs/PVA composites compared to lignin/PVA composites. The mechanical properties of the lignin/t-MWNT/PVA NFs could be preserved even after the heat treatment of PVA, which is a necessary process for medical applications such as wound healing on the skin’s dermal layer.