Tests/examinations are assumed to be powerful determiners of what happens in classrooms and it is commonly claimed that tests affect teaching and learning activities. The influence of tests on teaching and learning is often referred to as 'washback '. The purpose of this study was to investigate the washback effect of the Primary School Leaving Certificate (PSLC) English examination on teaching and learning of English language. The participants of the study were six grade eight English teachers, hundred grade eight students, and hundred grade nine students. The instruments used to collect data were document analysis, questionnaire, and interview. After the data were collected through these instruments, the findings were analyzed quantitatively and qualitatively. Findings of this study indicated that the Primary School Leaving Certificate (PSLC) English examination does not adequately reflect the contents of the textbooks. The study also showed that the Primary School Leaving Certificate (PSLC) English examination influences teachers' focus to the contents to be taught, and their way of preparing classroom tests/examinations. Moreover, the study indicated that students' attention to different contents of the English language is influenced by the Primary School Leaving Certificate (PSLC) English examination. Based on the findings, the researcher recommends that all contents need to be included in Primary School Certificate (PSLC) English examination, priority need to be given for the attainment of the objective of the course, there need to be a means for classroom tests to take part in selecting students to the next grade level (grade nine), and teachers need to be given instruction about 'washback '.