The study was conducted at Wonji town, which is located 110 km south eastern of Addis Ababa. The objective of the study was to assess bacteriological and chemical drinking water quality and related impacts on public health. Laboratory analyses of drinking water samples, questionnaires and relevant secondary data were used to generate important information from the study. Drinking water samples were collected using standard procedures from pipes, river and house hold water containers and analyzed for coliform bacteria using MPN techniques and nitrate, nitrite, ammonia and fluoride using spectrophotometer. The data were analyzed using SPSS software, t-test. Average counts of TC and FC for the water samples from house hold containers ranged from 9-126.5 MPN/100 ml and 0-23 MPN/100 ml, respectively. For the water samples from pipes and river, the average counts of TC and FC were 1.5-102 MPN/100ml and 0-22.5 MPN/100ml.The average concentrations of the chemical parameters from analyzed water samples at the study area were 0.01-0.76 mg/l, 0.0015-0.025mg/l, 1.1-6.15 mg/l and 2.3- 5.8mg/lfor ammonia-nitrogen, nitrite-nitrogen, nitrate-nitrogen and for fluoride respectively. Among analyzed drinking water samples, 70%, 90% and 100% of the samples were above the WHO recommended guideline limits for TC, FC and fluoride respectively. There fore, based on the results of most water samples, the water is non-potable from bacteriological and chemical quality points of view. The presence of high counts of total and fecal coliforms in the water samples could indicate the fecal contamination and probably the presence of pathogenic organisms in the water that could cause health risks to the community. Out of 128 Wonji high school students selected for the study through questionnaires, 92 (71.88%) of them were affected by dental fluorosis. Generally, the results of the study revealed that drinking water quality was deteriorated and caused public health problems. There fore, effective chlorination and defluoridation of water supplies are very important to improve the drinking water quality and the health of the community at the study area.