The removal of heavy toxic metals from industrial effluents is extremely important, especially for mercury (Hg), which is classified as a highly toxic even at low concentrations. For this purpose, novel thiourea chelating resins were synthesized as sorbent for Hg (II). Six different polymers of formo-phenolic types were characterized and evaluated for their chelating properties with respect to Hg (II) extraction. Batch adsorption studies of mercury (II) as a function of pH, initial metal ion concentration, temperature, and time showed that thiourea formo-phenolic polymers have a good affinity for Hg removal and a high adsorption capacity. Adsorption isotherms (Lang-muir and Freundlich) and kinetic models (pseudo-first and pseudo-second order) were used to interpret the sorption behavior of the materials. The Langmuir model yielded the best fit with a maximum adsorption capacity of 300 mg/g. Desorption studies were performed with aqueous thiourea solution and showed that the adsorbent is indeed regenerable and can be effectively used for up to three adsorption-desorption cycles with negligible loss of performance. This study confirmed the potential of thiol-modified formo-phenolic resins in sorbent engineering with promising applications in the remediation of mercury-contaminated water.