In this review article, synthesis, properties and applications of polyaniline-based nanocomposites (PANI-NCs) have been described. Different methods (viz chemical, electrochemical, photochemical and mechano-chemical) and size confinement tools used for preparation of PANI-NC are described with their advantageous and disadvantageous features. On the basis of synergized electrical, magnetic, optical, mechanical and thermoelectric properties, PANI-NCs are used in development of sensors, support catalysts, water purifications, energy and biomedicals. Further, applications of PANI-NC are elaborated with suitable examples centring on the role of nano-confinements and chemical modification along with existing challenges for commercial uses.