The intent of this study was to assess the Prevalence of Plagiarisms and its implication to quality of education: The case of Addis Ababa University. Both quantitative and qualitative data were collected through questionnaires, interviews and participant’s observers. A sample of eight departments was selected randomly among 40 postgraduate studies. A sample of 163 students participated from 483 postgraduate students of regular and extension program; besides 9 instructors were interviewed. The data were analyzed using Percentages, means and standard deviation. The findings reveal that internet plagiarisms and plagiarisms due poor understanding of in text citation, paraphrasing and referencing prevail most due to intentional plagiarism act of pressure to succeed and unintentional act of poor understanding of in text citation, paraphrasing and referencing conventions. Further, absence of vivid and inclusive mechanisms to identify the authenticity of students work across the selected departments show that there is a loosen ant-plagiarism movements in the departments. Therefore, this study suggests different recommendations and the main ones are departments and institutes should prepare common explicit simple examples of correct text acknowledgements conventions that could be put on the course outlines of each courses/modules; the nation higher educations should have a hub data base and software’s that could help instructors a cross the nation to check their students work with others prior work; student’s papers and thesis titles have to be guided to new issues and contemporary problems of the society to minimize replications and scrabbling on similar arena