Paul (2010) defines information system (IS) as it refers to a system of people, data records and activities that process the data and information in an organization, and it includes the organizationâ€Ÿs manual and automated processes. Information system can be applied in different social, economic, political and organizational contexts to facilitate the day to day activities of institutions in the world. rnThe objective of this study was to investigate the factors influencing /affecting the adoption of information system at Addis Ababa Water and Sewerage Authority. Due to the scarcity of studies on the influence of information system on water and sewerage authorities, the study aimed to investigate factors affecting information system adoption in these institutions. rnFor a better understanding of the situation a quantitative research approach was employed. Questionnaire was used as means of data collection. The quantitative data generated was analyzed using descriptive and inferential statistics with the help of Statistical Package for Social Sciences (SPSS). Frequency, mean, standard deviation, correlation and regression were used for analyzing the quantitative data. The study was guided by technology acceptance model. From the finding all the independent constructs (Perceived Usefulness (PU), Perceived Ease of Use (PEOU), Information System Strategy (ISS), Information System Infrastructure (ISI) and Information System Awareness (ISA) and dependent construct (Behavioral Intentions to Use) show or demonstrate a positive inclination of employees towards the behavioral intension and actual usage of information system. Moreover the study indicates that infrastructure and Budget are the main challenges to adopt information system at AAWSA.