The main objective of this study is to assess the success of ERP post-implementation at Ethiorntelecom. The general approach of this research was a case study in which a combination ofrnquantitative and qualitative methods has been used to collect and analyze data. The quantitativerndata was collected using questionnaires from sample population of 320 users from HR, Financernand sourcing & facility departments with different job positions, roles, and work experience. Therncollected data was analyzed using SPSS. In the qualitative study, direct interviews were used torncollect data from three executive management members of Ethio telecom. A theoretical ERP successrnmodel was used to assess the success of ERP Post- implementation at Ethio telecom. The results ofrnthis study show the deployed ERP system has brought significant impact on individualrnperformance by enhancing employee awareness and recall of job- related information, increasedrnemployee productivity and decision-making activities during post-implementation phase.rnSimilarly, the study report shows there is positive impact in organizational business processrnmanagements by integrating and improving internal communication, providing accurate & realtimerninformation, increasing efficiency and productivity, reduces administrative and operationsrncosts, and resulted better positioning for e-government and online business transactions. Evenrnthough ET has gained many benefits from deployed ERP system, some challenges werernencountered during post implementation phase. Among those challenges ERP system responserntime delay (slow response), ERP system data integration with other ET soft-wares, ERP system isrnnot always up and running as necessary, lack of training & IT-helpdesk support to solve thernproblem were the main challenges during post implementation phase. Hence, the researcher hasrnrecommended that Ethio telecom is expected to resolved challenges of ERP system interruptions,rnERP data integration, ERP system slow performance, ERP system flexibility, lack of adequaterntraining and IT-help desk support as top priority to get the full-fledged benefits from deployedrnERP System.