Nitrate is one of the most widespread chemical contaminants found in groundwater across the globe. The best known and documented human health risk associated with high levels of nitrates in drinking water are methemoglobinemia and carcinogenetic due to N-nitroso compounds (NOC. Adsorption is one of the most reliable and cost-effective method to remove nitrate contaminants from drinking water obtained from groundwater. The natural zeolite was taken from Southern Nations, Nationalities, and Peoples’ Region (SNNPR) and modified with ferric chloride (Fe-NZ). The nature and morphology and elemental composition of sorbent was characterized by XRD, SEM/EDX and Elemental analysis. The obtained results showed that the maximum percentage of nitrate adsorption attained at equilibrium pH = 5, after 120 min of contact time, at a temperature of 25 oC, initial concentration of NO3--N 11.3 mg/L, agitation speed of 200 rpm and with an adsorbent dose of 1.5 g/100 ml was 89.56%. Experimental data has been analyzed using the Freundlich and Langmuir isotherm fits the experimental data very well and this confirms the monolayer coverage nitrate ion onto modified zeolite particle. The maximum monolayer adsorption capacity of modified natural zeolite was found to be 7.67mg/g at the optimized parameters. Therefore; the experimental results showed that application of Fe-MNZ is a good adsorbent for treating groundwater that was contaminated with nitrate.