The quality management system has affirmative effects on the operational endeavors of the organization. Itprovides consistency of processes, consistency of products and procedures through integrating all activities and functional units of the organization to achieve organizational goals and objectives. There are many organizations which have got a certification of ISO 9001QMS implementation in the leather manufacturing in Ethiopia. However; they did not overtake the systems as a quality improvement tool for continuous improvement of their performance. Moreover; The QMS implementation could not be accomplished according to ISO 9001 QMS principles and requirements. This is because the organizations have misunderstood its purpose and benefits.The main purpose of this studyis to investigatethe effects of QMS implementation practice on organizational performance and market competitiveness at ELICO-Awash tannery which is among a few leather manufacturing industries certified for ISO 9001:2008 QMS.It also identifiedthe problems and challenges of QMS implementation practice in ELICO-Awash tannery.the conceptual frame work of this studyis based onthe principles of QMSto investigateitseffect of QMS implementation practice on the organizational performance and market competitiveness.A descriptive research method isusedconducting the research and purposive sampling method is used for determiningthe respondents.Questionnaires and interviewswere used instruments for collecting of primary data based on the implementation practices of ISO 9001:2008 QMS. The results analyzed and interpreted quantitatively using five-point Likert scale and IBM SPSS statistics version 22 software. Descriptive and inferential statistics were used to carry out forfurther data analysis and interpretationstatisticallytesting of manifesting the effects of QMS on the organizational performance and market competitiveness. The results revealed that the QMS principles which are predicator variables, have strong and a positive correlation with the organizational performance and market competitiveness. The model of multiple linear regression has shown that the QMS has explained its effect on the variance of organizational performance and market competitiveness. Key words: QMS, ISO 9000 standards, QMS principles, organization performance and market competitiveness.