In this study, adsorption behaviors and mechanisms of Sb(III) ions onto Fe(III)-treated humus sludge adsorbent (FTHSA) from aqueous solutions was investigated using batch adsorption techniques, Fourier transform infrared (FT-IR) spectra and scanning electron microscopy were coupled to an energy-dispersive spectrometer (EDS). FTHSA was prepared via immersion with 1 mol/L FeCl3. The effects of dosage, contact time, Sb(III) initial concentration, and pH on the adsorption of Sb(III) onto FTHSA were investigated. Sb(III) adsorption was favored at pH with 2.0 and decreased dramatically with increasing pH. The description of equilibrium data of Sb(III) adsorption by Langmuir, Freundlich, and Dubbin-Radushkevich isotherm models showed that Langmuir model provided the best fit for Sb(III) adsorption with maximum adsorption amount of 9.433 mg/g. Pseudo first-order, pseudo second-order, Elovich, and intraparticle diffusion model were applied to describe the adsorption process of Sb(III) ions onto FTHSA. The results showed that the pseudo second-order model described well how Sb(III) adsorption and chemical adsorption played a dominant role in the adsorption process. The FT-IR spectra also indicated that the chemical interactions as ion exchange among the metal ions and N-H, O-H, C=O, COO, and C-O were mainly involved in the adsorption process. Therefore, FTHSA has a suitable potential removal for Sb(III) ions in the practical process.