The anticoccidial monensin (MON) is a high-concern emerging pollutant. This research focused on six low-cost bio-adsorbents (alfa, cactus, and palm fibers, and acacia, eucalyptus, and zean oak barks), assessing their potential for MON removal. Batch adsorption/desorption tests were carried out, and the results were fitted to the Freundlich, Langmuir, Linear, Sips, and Temkin models. The concentrations adsorbed by the six materials were very similar when low doses of antibiotic were added, while they differed when adding MON concentrations higher than 20 µmol L⁻¹ (adsorption ranging 256.98–1123.98 μmol kg⁻¹). The highest adsorption corresponded to the sorbents with the most acidic pH (<5.5) and the highest organic matter and effective cation exchange capacity values (eucalyptus bark and acacia bark, reaching 92.3% and 87.8%), whereas cactus and palm fibers showed the lowest values (18.3% and 10.17%). MON desorption was below 8.5%, except for cactus and palm fibers. Temkin was the model showing the best adjustment to the experimental data, followed by the Langmuir and the Sips models. The overall results indicate that eucalyptus bark, alfa fiber, and acacia bark are efficient bio-adsorbents with potential for MON removal, retaining it when spread in environmental compartments, reducing related risks for human and environmental health.