The aim of this study is to reduce ammonia concentration in tannery wastewater using bagasse fly ash in a batch adsorption system. Experiments were conducted to study the effect of various parameters such as adsorbent dose and contact time. Data analysis was performed by calculating the efficiency of adsorption and fitting the data into Freundlich and Langmuir isotherm models. Correlation coefficient and mean squared error were used to evaluate the performance of the models. From the results, it was found that the operating conditions to achieve an optimum removal efficiency of 45.72% are 1 hour contact time and 2 grams of bagasse fly ash. The results also indicate that the data fits Langmuir model well where Langmuir constant Q o , b, and correlation coefficient were found to be 0.706 mg/g, 0.209 L/mg, and 0.9424, respectively.