AbstractThe objective of this study is to investigate the English as Second Language teachers’ knowledge and ability in implementing School-Based Assessment (SBA). It is also to identify the challenges and their recommendations to improve its implementation. A qualitative research design was chosen to answer three research questions. Three sets of instruments were utilized to measure teachers’ knowledge and ability. Seven ESL teachers were selected as purposive sampling in the study from two secondary schools which were selected from one of the districts in Selangor. This case study participants were employed to be in the interview to gain a better insightful explanation on the challenges and suggestions of the implementation of SBA. The data were collected through semi-structured interviews, observations and document analyses. The findings of the study indicated that the teachers had insufficient knowledge and ability to implement School-Based Assessment effectively in schools. Some of th.....