Dental and skeletal endemic fluorosis continue to be a public health problem in several parts of the world including Ethiopia (especially in the Rift Valley Region), where drinking water contains fluoride much higher than the WHO permissible limit (1.5 mg/L). Development of appropriate defluoridation technologies is important in developing countries like Ethiopia to mitigate the irreversible health impacts of fluoride in drinking water. In this study, manganese oxide modified aluminium oxide hydroxide (MOAOH) was prepared from manganese (II) chloride and aluminium oxide hydroxide and its fluoride removal capability has been investigated. The parameters considered were effect of percentage of manganese oxide, adsorbent dose, contact time, initial concentration of fluoride, and initial pH of the water. Removal efficiency of the adsorbent varied significantly with percentage of manganese oxide with an optimum value of about 11% of manganese oxide in the adsorbent. The removal efficiency increased with increasing adsorbent dosage. It was found that the optimum dose is 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Adsorption capacity showed an increasing trend with an increase in initial fluoride concentration in the water. The removal of fluoride by MOAOH also varied with the initial pH of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. At optimized conditions removal efficiency exceeding 96% was achieved under the experimental conditions used in this study. The adsorption data was analyzed using the Ferundlich, Langmuir, and D-R models. The results showed that the experimental data can be well described these models. The minimum adsorption capacity obtained using the Ferundlich isotherm model is 4.48 mg F-/g and the maximum capacity from the Langmuir isotherm model is 18.62 mg F-/g. The mean free energy estimated from the D-R model is 9.71 kJ/mole, suggesting that the adsorption process is primarily chemisorption. The kinetic analysis showed that the adsorption is well described by a pseudo-second order reaction model with an average rate constant of 3.4689 x 10-2 g min-1 mg-1. The adsorbed fluoride could be easily desorbed by treating with 1.0% NaOH solution. It is concluded VIII that, MOAOH is highly promising adsorbent for removal of excess fluoride from drinking water.