In this study, poly(4-aminophenol) was successfully prepared by an enzymatic reaction in water, with its molecular weights ranging from 12,000 to 52,000. The polymerization of 4-aminophenol produced high yields over a wide pH ranging from 4 to 10. In addition, poly(4-aminophenol) was also used for silver-ion adsorption because it was composed of amino and hydroxyl groups. We found that the adsorption capacity of poly(4-aminophenol) was relevant to the time, pH value, temperature, and concentration of silver ions, and the greatest adsorption capacity of poly(4-aminophenol) for silver ions was 220 mg/g. Moreover, a series of tests showed that the adsorption of silver ions was mainly achieved by a reduction reaction, and the silver nanoparticles were formed with a face-centered cubic structure, and their average particle size was about 10 nm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40367.