Removal of industrial dyes and metals into water has been considered as a serious environmental problem. To solve this issue, in this study nickel hydroxide/polystyrene composites adsorbents were introduced for the water remediation from the harmful methylene blue dye and Fe (III). Polystyrene was obtained from its monomers using emulsion polymerization technique. The composite was obtained by precipitating nickel hydroxide from its solution on polymer surface by enhancing pH of the medium. The structural and morphological characteristics of the synthesized composites were investigated by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energetic dispersive X-ray (EDX), and x-ray diffraction (XRD). FT-IR spectra for composites showed the characteristic peaks of polystyrene and that correspond to hydroxide from NiOH2 (3442 cm-1). SEM analysis showed that the Ni(OH)2 were distributed on the surface of polystyrene in a regular manner. EDX analysis showed the presence of 19.9 wt% of Ni on the composite. XRD analysis showed the characteristic diffraction peaks at 2θ = 19.54 corresponding to polystyrene and at 2θ = 32.5, 38.5, 52.1, and 58.97 corresponds to Ni(OH)2. The composite was tested as an adsorbent using the batch technique. The impact of solution pH, contact time, and absorbent dose on the adsorption processes were studied to optimize the operational parameters. Kinetic and equilibrium studies showed that the adsorption processes followed pseudo-first-order kinetic and Freundlich isotherm. Maximum adsorption capacities of 32.73 and 58.24 mg g-1 were achieved in case of MB and Fe (III), respectively. Thermodynamic studies showed that ΔG values for the adsorption processes ranged from -0.075 to -1.435 kJ mol-1 by changing temperature from 303K to 343 in case of MB; ΔG values ranged from -0.467 to -1.548 kJ mol-1 by changing temperature from 303K to 343 in case of Fe (III). Negative values ΔG revealed that the adsorption processes were spontaneous and feasible. Hence, nickel hydroxide/PS composites could be potentially used for treating wastewater from MB and Fe (III).