Free radicals in tobacco smoke trigger numerous lung diseases, which are worldwide health considerations. The ideal free-radical, tobacco-smoke scavenger must be highly reactive and temperature resistant. Catalases (CATs) show attractive potential to scavenge free radicals in tobacco smoke, because of their higher reaction rate compared to that of non-catalyzed reactions. Their fragile nature, however, diminishes their catalytic activity in hot tobacco smoke. Therefore, it is essential to enhance the structural integrity and catalytic stability of these enzymes under severe environmental conditions. In order to improve the thermal stability of CATs, we have developed a facile approach to produce CAT nanocapsules (nCATs) by encapsulating a single enzyme in a polyacrylamide (PAAM) shell. The rigid polymer shells on the CATs surface prevents their free deformation. The secondary structure of the enzyme is retained and their dissociation is almost nil even under high operational temperatures. As a result, the structural stability and thermal resistance of the enzyme are significantly enhanced. The nCATs are covalently bound on cellulose acetate fibers to enable the enzyme sticking to the cigarette filters.The electron paramagnetic resonance (EPR) and Saltzman procedure reveal that the nCATs are able to efficiently scavenge 90% of the free radicals in tobacco smoke. The use of such nCATs with improved enzyme thermal stability opens up new opportunities for future application in cigarette filters.