Efficiently chemically modified adsorbents based upon palm fibers were prepared through chemical treatments of palm fibers by sulfuric acid (PF-AC), oxalic acid as a chelating agent (PF-Chel), HNO3 as an oxidizing agent (PF-OX) and Na2SO3 as a reducing agent (PF-Rd). The four produced adsorbents were applied for the removal of Pb(II) and Cd(II) from synthetic waste solutions. The removal capacity of all chemically modified adsorbents has been investigated through the batch tests to determine the optimum parameters for maximum removal. The kinetics and isotherm studies have been applied to identify the adsorption type. All data in this work has been used as determining factors to predict the adsorption process mechanism. The characterization of the surface of the chemically modified adsorbent [FTIR and SEM] was also studied as another contribution to proving the suggested adsorption mechanism. Experimental data were best fitted by Langmuir model while kinetic results were appropriately expressed by the pseudo-second-order model. The results demonstrated the highest capacity values of 56 and 33 mg/g using PF-Rd for both Pb (II) and Cd (II) ions, respectively. Throughout this study, PF-Rd and PF-OX achieved the maximum capacity with the adsorption of both heavy metals.