In this study, kapok fiber structure-oriented polyallylthiourea (KF-PAT) has been approached via a facile in situ preparation and then used as the adsorbent to entrap Au(III) ions in aqueous solution. During this process, an efficient adsorptive reduction with the conversion of Au(III) into metallic Au nanoparticles (NPs) was observed using KF-PAT as the adsorbent. This conclusion was successfully confirmed by means of X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The conversion of Au(III) ions into Au NPs was achieved without the assistance of any external reducing agents and the resulting Au NPs were uniformly dispersed into the polymer matrix, as supported by the observation from transmission electron microscopy (TEM). Finally, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with an excess amount of NaBH₄ was used as a model reaction to evaluate the catalytic performance of Au NPs-loaded KF-PAT.