This study introduces a facile enzymatic reaction approach to the synthesis of red algae (Gelidium amansii) microfibers. Through use of a suitable cellulase enzyme, entangled red algae fiber networks could be divided into single microfibers, which enlarges their surface area and generates more hydroxyl groups on their surfaces. The microfibers obtained after this enzyme reaction showed an excellent ability to take up heavy metals; in fact, the absorption efficiency was reversely proportional to fiber length. Under optimal conditions, these microfibers reduced their length and size deviation to ~92% and ~95%, respectively, at which the heavy metal absorbance efficiency increased to ~230% compared with that of red algae biomass. It was also found that solution pH affected the heavy metal adsorption behaviors due to a change in charge density; maximal heavy metal adsorption of heavy metals was observed at pH 9. These results highlight that our algae microfibers produced using the biofriendly enzyme reaction could be utilized as an effective remover of harmful species from water media.