Service quality and customer satisfaction are very important concepts that companiesrnmust understand if they want to remain competitive and grow. In todayâ€™s competitivernenvironment delivering high quality service is the key for a sustainable competitivernadvantage. The purpose of this study is to assess the service quality and customerrnsatisfaction of Oromia International Bank by using a descriptive research type that usedrnquantitative research method. The target population of the study was customers of OIB inrnAddis Ababa region where 385 samples were selected for the study. A survey has beenrnused to collect primary data and 302 questionnaires were used in final analysis. Validityrnand reliability testing were employed to identify service quality attributes. Study resultsrnshow that service quality is at the root of customer satisfaction. The findings of the studyrnrevealed that the overall mean score of perception is higher than expectation inrntangibility and assurance dimensions, yielding a positive SERVQUAL gap, reliability andrnassurance were resulted in a negative and the responsiveness has a zero gap. Thernattributes perceived satisfactory performed are scattered between the five service qualityrndimensions. The most affirmatively perceived service quality dimensions are assurancernand responsiveness followed by reliability. However, empathy and tangibility are lessrnperceived compared to the other dimensions. Responsiveness shows the highest positiverncorrelation with overall customer satisfaction and tangibility demonstrates the secondrnhighest positive correlation with overall with customer satisfaction. The result of thisrnstudy provides evidence that the SERVQUAL dimensions are a useful tool to predictrnoverall customer satisfaction for OIB. Further analyses on the assessment of servicernquality and overall customer satisfaction OIB is a topic to be researched. Continuousrnapplication of the assessment will allow a comparison between the results and furtherrndiagnostics of the service quality.