Language teachers' assessment literacy has been a much debated subject in the educational arena recently. Teachers' assessment knowledge base and skills, important aspects of their assessment literacy, have been extensively investigated at the school level; however, the research on this subject in the tertiary EFL context remains underdeveloped. This study reports findings of tertiary EFL teachers' assessment literacy in terms of their assessment knowledge base in the context of Saudi Arabia. The study is informed by sociocultural theoretical background, with pragmatism as the philosophical underpinning. It uses an adapted instrument called Classroom Assessment Literacy Questionnaire, and the data are obtained from 80 questionnaire respondents. The statistical analysis of the data revealed that tertiary EFL teachers' current assessment knowledge base is very limited and not consistent with the contemporary trends and approaches to educational assessment in terms of their preparation and readiness for the continuously mounting challenges posed by classroom-based assessments. These results indicating gaps and inadequacies in tertiary EFL practitioners' assessment literacy have strong implications for teacher development in the area of assessment and testing at the level of policy, practice and professional development programmes.