The engineered nano or atomic scale catalysts have revolutionized the domain of catalysis by providing high selectivity and activity with long term stability, raising hope for sustainability for industrials applications . However, noble metal catalysts, commonly utilized are too precious to make them viable for commercial operation. Therefore, nanoengineered catalysts using low-cost elements (transition metal elements), which must be endowed with high stability and efficiency, are the need of the hour. In this regard, different types of materials are under active consideration as well as investigation, revolutionizing the catalytic science to meet the novel requirements, including graphene for HER reaction , electronic waste as a catalyst for water splitting , carbon dots for ORR and OER reactions etc. However, limitations exist, such as the yield of the catalyst preparation, lack of efficiency, and lower selectivity, which requires the design and development of new catalysts A new concept called entropy stabilized multicomponent alloys, popularly known as high entropy alloys has emerged and reported to be successful in design of novel catalysts for variety of reactions . The five or more elements are mixed in equiatomic or near equiatomic ratio to form single-phase alloys, which has recently been used to design novel catalysts . They have shown tremendous potential due to their vast compositional space comprising almost all the metallic elements in the periodic table, allowing us to tune the chemistry and surface microstructure and provide the unlimited scope of design new multipurpose catalysts. Among the low-cost metals available in the periodic table, the alloys made of 3d-transition metals (TMs) are considered to be the best candidates for the nanoengineered HEA catalysts . The four-core effects of HEAs impart exceptional properties; high entropy providing the single-phase stabilization, sluggish diffusion imparting long-term stability, cocktail effect altering their d-band centre with respect to Fermi energy level, and the lattice distortion modifying energy levels of free electrons . Therefore, the high entropy alloys (HEAs) are expected to provide an active catalyst because a single-compositional alloy can exhibit multiple reactions due to multielemental bonds dangling over the surface with a unique surface electronic structure favourable for the adsorption . This allows the design gamut of the chemistry of high entropy catalysts with different elements for their electrochemical responses. This includes degradation of azo dyes using AlCoCrTiZn HEA catalyst , converting CO 2 into highly reduced hydrocarbon (CH 4 , CH 3 OH) using AgAuPdPtCu HEA catalyst , formic acid and methanol to hydrogen fuel . The NH 3 decomposition using high entropy alloy (CoMoFeNiCu) was 20 times higher than the pure Ru catalyst . CO oxidation reaction, one of the important yet simple exhaust treatment reactions, has not extensively been studied on the high entropy catalysts. Preferential CO oxidation is important to purify hydrogen gas where CO concentration of lower than 5 ppm is required . Supported Pt catalyst is the most widely used one for this reaction although the cobalt-based catalysts exist, providing ultra-low temperature activity . Among various materials used for this reaction are supported metal oxides, perovskite, spinels, substituted metal oxides etc . Among the emerging class of materials, HEAs can possibly outperform previously known catalysts for CO oxidation reaction. However, the magic chemistry is still unknown as a low volume of work exists for CO oxidation reaction on HEAs . In fact, a basic kinetic investigation is not reported so far, which can, in principle lead to a fair comparison of HEAs with the conventional catalysts. In this work, we have explored the CO oxidation activity on low cost easily scalable CoFeZnNiGa HEA nanoparticles. The kinetic parameters have been estimated and compared with the other known catalysts in the literature. The nanocrystalline CoFeZnNiGa HEAs has been prepared by the method of cast-and-crushing, involving cryomilling of the cast alloy ingot at extremely low temperature . Therefore, the surface of the catalyst remains native or uncapped due to low temperature milling, making it viable for catalytic applications . Further DFT calculations were done to find the active site over the HEA surface along with the probable mechanism, where mainly the effect of suitable orbital overlap among the HEA and reactant molecule was considered.