Carbon-based nanocomposites (CNC) are compounds that are characterized by extraordinary properties and have a broad range of potential uses in the scientific and technological areas. This chapter looks into several carbon-based nanomaterials, including graphitic carbon nitride (g-C3N4), graphene, carbon nanotubes (CNTs), carbon nanofibers (CNFs), and carbonized biomass nanofibers. It starts with a review of the published paper. The synthetic technique, photoluminescence mechanisms, and potential uses of these carbon nanomaterials receive particular attention. Along with this, this chapter provides in depth knowledge regarding carbon nanotubes and their importance on modern applications. We outline synthesis methods for graphene-based nanocomposites and their applications in EMI shielding, sensing, drug delivery, optoelectronics, and anticorrosion coatings. The roles of carbon-based nanocomposites in environmental remediation, bioimaging, and sensing are likewise examined. This chapter discusses CNF properties and their application in energy storage devices, environmental remediations, and supercapacitors and examines the graphitic carbon nitride synthesis technique and applied on various organic transformations. The chapter also highlights carbonized biomass nanofibers as a sustainable alternative for eco-friendly photoluminescent materials, contributing to the development of green technologies.