Since 2005, Indonesia has administered the National Examination (NE), from which the result is used as a basis to decide the students' exit from secondary schools. As a high stake testing, the NE has caused various washback effects, both positive and negative. Consequently, the existence of the NE has been accompanied by heated debates and controversies. The pros believe that the NE may improve secondary education standards, while the cons argue that the NE will create injustice and unnecessary anxiety among the students. However, both the pros and cons base their arguments on common sense not supported by a sound reasoning. The present study tries to explore the washback effects of the English National Examination (ENE) in Indonesian secondary education context, involving three Secondary Schools categorized based on their NE achievement. The results of the study indicate that English teachers and students from the schools involved have different perceptions on the ENE. The English National Examination has an influential impact on teachers' teaching in the aspect of: activity/time arrangement, teaching materials, teaching contents, teaching methods, teaching strategies, ways of assessing, and on the feelings and attitudes of the students. The ENE also affects the students' learning in the classroom in which teachers mainly teach to test, practice the test and develop test-taking strategies. The dimensions of the washback effect of the ENE on both English teachers and students are negative and positive, strong, specific and for a short period time.