Studies in the field of heavy metal ion removal from industrial wastewater using biomass are increasing in number due to highly efficient and cost-effective applications. In this study, we report the use of non-living lichen, Ramalnia fraxinca, as a biosorbent for the removal of Cu(II) and Ni(II) ions from aqueous solution. The biosorption of Cu(II) and Ni(II) ions from aqueous solution by R. fraxinea biomass is investigated in a batch system for parameters such as pH, contact time, and initial concentrations of metal ions. The kinetic data of the biosorption process is evaluated with pseudo-first-order, pseudo-second-order and intra particle diffusion kinetic models. The experimental data shows greater accordance with the pseudo-second-order model for the tested ions. The equilibrium data of Cu(II) and Ni(II) ions biosorption fitted onto both the Langmuir and Freundlich adsorption models. The highest sorption capacities of Cu(II) and Ni(II) ions by the R. fraxinea biomass are found to be 43.48 and 9.71 mg/g, respectively. The biosorption studies indicate that R. fraxinea biomass is a moderate biosorbent for the removal of Cu(II) and Ni(II) ions from aqueous solutions compared with other biosorbents.