The current study aimed to explore junior secondary school English as a foreign language (EFL) teachers perceptions of classroom-based assessment and to understand the extent to which teachers' perceptions are reflected in their practice. To this end, a total of twenty two Indonesian EFL teachers from six public junior secondary schools participated in the study where they were surveyed and interviewed. Shim's (2009) survey instrument was adapted to collect data related teachers' perception. A semi-structured interview was conducted with five of twenty-two teachers where were selected randomly. A document study was also conducted to further verify data from the questionnaire and interview. The gathered data included curriculum, syllabus, lesson plans, example of assessment materials and students' work. Quantitative data analysis with t-test was employed to analyse the quantitative data while the qualitative data were analysed using a thematic data analysis. Findings of the current study had suggested that teachers had appropriate knowledge about assessment principles and applied such a knowledge into classroom practice. Although, the discrepancy between teachers' knowledge and its application in classroom practices was identified, particularly in implementation and monitoring stages. Some concerns that influenced teachers' practice of classroom assessment included the local or school policy, teachers' use of nonachievement factors (e.g. students' attendance and attitudes), and parents' involvement in their children education. The findings contribute to a better understanding of teachers' assessment literacy in their particular context, as they make meaning and interact with assessment materials and relevant stakeholders of assessment. Recommendations were offered in reference to the findings.