Aims: The objective of this study was to evaluate phenol removal from a synthetic solution using modified zeolite (clinoptilolite) with FeCl 3 as an adsorbent. Materials and Methods: The zeolite samples were crushed and granulated using standard ASTM sieves (mesh size of 20). The prepared zeolite then was modified by FeCl 3 . The chemical composition and the surface area of the zeolite were analyzed using XRF and N 2 gas via BET isotherm and Belsorb software. In this study, different parameters including pH (3, 7, and 12), initial concentration of phenol (25-200 mg/l), contact time (20-240 min) and the amount of modified zeolite (0.25-3 g/l) were examined in a batch reactor. The concentration of phenol was measured at wavelength of 500 nm by a spectrophotometer. Results: The results of this study showed that as the initial concentration of phenol, the adsorbent dose and the pH in the range of 3-12 increased the adsorption / removal of phenol increased. Phenol adsorption equilibrium was achieved within 100 min contact time and the optimum pH for adsorption of phenol using zeolite was found as 3. The adsorption data complied with Langmuir isotherm (r 2 =0.98). Conclusions: The results showed that modified zeolite can be used effectively in removing phenol. The removal efficiency of phenol in lower pH was more than in higher pH. Also, due to the low price of the zeolite and its simple modification, it can be used for removing hazardous pollutants in water and wastewater.