Electrospun nanofibers have emerged as transformative materials due to their unparalleled surface-to-volume ratios, tunable porosity, and excellent mechanical flexibility, making them suitable for energy storage, catalysis, biomedicine, and environmental remediation. However, their inherent surface limitations—poor chemical stability, insufficient active sites, and limited functionality—restrict their full potential. Chemical vapor deposition (CVD) has risen as a game-changing post-synthesis modification strategy, enabling atomic-scale precision in surface engineering. This is also impactful for carbon-based nanofibers, where surface inertness limits their electrochemical performance. This review critically examines advanced CVD techniques, including atomic layer deposition (ALD), plasma-enhanced CVD (PECVD), and initiated CVD (iCVD), which enable the formation of conformal coatings, hierarchical functionalization, carbon nanotube integration, and interfacial optimization of as-spun nanofibers. We highlight breakthroughs in hydrophobicity, catalytic activity, biocompatibility, and energy storage performance, with applications ranging from oil–water separation to nerve gas detoxification, pH-responsive drug delivery, and high-capacity carbon-composite lithium-ion batteries. By dissecting deposition mechanisms, material innovations, and emerging applications, this work highlights the synergy between as-spun nanofibers and the exploitation of CVD techniques in designing versatile materials. Furthermore, advancements hinge on computational modeling, novel precursors, including carbon-rich sources, and scalable processes to bridge lab-scale innovations with industrial deployment are desired. This comprehensive analysis provides a guiding framework for researchers utilizing CVD techniques as a post-modification tool to develop nanofiber-based solutions addressing global challenges in sustainability, healthcare, and energy.