Polyaniline (PAni), cellulose fiber (CF) and a PAni–CF composite, which were characterized by infrared spectroscopy, scanning electron microscopy and thermogravimetry, were investigated in adsorption studies of meloxicam (MLX) from aqueous media. PAni-deposited CF composites were prepared via in situ polymerization. These materials were assessed with varying pH, contact time between the adsorbent and adsorbate, and concentration. Kinetic data were evaluated by pseudo first- and second-order, Elovich and intraparticle diffusion models, and the concentration data were evaluated by Langmuir, Freundlich, Sips, single-site Langmuir–Freundlich and dual-site Langmuir–Freundlich models. MLX adsorption was better at pH 2, and the pseudo-second-order (R² ≥ 0.999) kinetic model and the Langmuir–Freundlich (R² ≥ 0.9901) isotherm model showed the best fit. PAni–CF composite was found to be the best adsorbent material compared to PAni and CF, because of the greater adsorption capacity (Q = 169.5 mg g⁻¹), which can be explained by the combination of the adsorptive properties of the two materials.