EMI is a 20th-century radiation pollution that not only results in various health hazards but also weakens the electronic system's performance. With the rapid global development in various fields, this problem is increasing consistently. To ensure the uninterrupted performance of electronic gadgets and avoid the effects on human health, EMI shielding has become a necessity. In the recent past, a large number of materials having a wide range of conductivity and good electromagnetic attributes have been exploited for EMI shielding applications. Initially used metallic shields, due to their high cost & weight, corrosion propensity, and reflection-based shielding, have been replaced by various types of materials. Among them, intrinsically conducting polymers (ICPs) like polyaniline, polythiophene, polypyrrole, etc., and their composites with various types of conductive and/or magnetic fillers have played a significant role. Among all the conducting polymers, polyaniline has been studied the most due to its special properties like moderately high conductivity, ease of synthesis, proton doping, low cost, and high environmental stability. Most of the developments related to EMI shielding have been focused on the synthesis of new materials with high shielding effectiveness (SE). For this purpose, polyaniline and its composites have been widely explored due to its appropriate properties. But the commercial use of polyaniline for EMI shielding applications has always been hampered due to its infusibility and limited processability. Also, limited work has been done for the fabrication of polyaniline composites in the form of sheets that have sufficient SE along with improved thermal and mechanical stability. The work presented in this chapter is based on the fabrication of lightweight, thin sheets of polyaniline composites for EMI shielding application in the X-band of microwave range (8.2-12.4 GHz). The polyaniline-CFnovolac (PACN) composite sheets thus obtained were finally tested for EMI shielding applications using vector network analyzer (VNA) in the X-band of microwave range. Characterization of all the composites and/or their sheets was done by UV-vis, FT-IR, SEM, TGA, electrical conductivity (standard four-probe method), flexural strength, and flexural modulus measurements.