Two activated carbons (AC) prepared from onion leaves (OL) (Allium fistulosum) and palm kernel shell (PS) (Elaeis guineesis) were used to adsorb phenol from aqueous solution. Adsorption kinetics was studied by Pseudo-first order (PFO) and Pseudo-second order (PSO) models, while equilibrium was modelled using Langmuir, Freundlich, Toth and Redlich Peterson isotherms. Adsorption mechanism was analyzed applying Boyd and intraparticle diffusion models. The parameters of each one of the models were calculated using Minitab17® by non-linear regression. Piecewise linear regression was applied to calculate the parameters of Boyd and intraparticle diffusion models. Phenol adsorption onto activated carbons is describe better by Langmuir isotherm and PSO kinetic model. Maximum adsorption capacity was between 30 and 40 mg.g−1.