Separation process based on polyamide (PA) thin film composite (TFC) membrane is the dominant desalination technology in the 21st century to produce potable water to meet the growing global freshwater demand. Despite offering good filtration performance and exhibiting stable chemical and mechanical properties, TFC membrane still encounters other technical challenges such as surface fouling and trade-off feature between water permeability and solute selectivity which prompt continuous research efforts. There has been growing interest in recent years among researchers to alter the surface properties of PA layer via various modification methods to overcome the drawbacks of typical selective layer. But the question that remains to be answered - Does the modified PA layer effective for performance improvement? It is the aim of this article to provide a comprehensive review on the modification techniques (i.e., surface coating, surface grafting, plasma treatment and layer-by-layer assembly) and the modifying materials (both organic and inorganic materials) that have been commonly employed to establish a functionalized layer atop PA layer to improve its characteristics for desalination process. We hope this review that covers the relevant articles published over the past 10 years could provide insights to scientists in modifying selective layer of TFC membranes for better performance in water treatment processes.