Textile surface modification and functionalization techniques are designed to induce controlled physicochemical changes at the fiber surface while maintaining the intrinsic bulk properties of the textile substrate. Precise characterization of these surface-specific changes is essential for understanding structure–property relationships. Surface-sensitive analytical methods are required to evaluate alterations in chemical composition, surface morphology, interfacial behavior, and nanoscale topography resulting from physical, chemical, and biological modification processes. Spectroscopic, microscopic, and interfacial measurement techniques play a critical role in quantifying functional group incorporation, surface energy variations, and microstructural evolution at the fiber interface. The chapter concisely describes commonly used instrumental analysis and characterization techniques with emphasis on wettability and surface energy evaluation, surface topology, surface chemistry, and functional property assessment.