As a natural nanotubular material, halloysite nanotubes (HNTs) offer advantages including low cost and excellent friction-reducing properties. Thus, developing new types of HNT-based composite nanomaterials is beneficial for further enhancing their friction reduction performance. Herein, we develop a novel water-based nanoadditive by fabricating chitosan-modified nanoflower-like molybdenum sulfide (MoS 2) grown on halloysite nanotubes (CS-NF-MoS₂/HNTs). Through a series of characterizations, we confirm the makeup and architecture of CS-NF-MoS₂/HNTs, where chitosan functionalization endows the NF-MoS₂/HNTs nanocomposite with better water dispersion stability. Tribological evaluations of CS-NF-MoS₂/HNTs added in water demonstrate significant reductions in friction coefficients (67%) and wear rates (55.45%) compared to pure water, even surpassing individual MoS₂, HNTs and NF-MoS₂/HNTs as nanoadditives. Friction improvement mechanism of nanocomposite as nanoadditive via worn surface characterizations reveals the occurrence of collaborative lubrication during boundary lubrication. This work establishes an underlying prospect of CS-NF-MoS₂/HNTs as nanoadditives in water-based lubricants with exceptional friction/wear reduction capabilities.