Assessment is an essential tool to measure students’ progress. It is paramount for teachers to understand their classroom assessment practices to make informed educational decisions. This study seeks to identify in-service and pre-service teachers’ understanding of knowledge and affective dispositions towards language assessment through two instruments: theEnglish Language Assessment Literacy Inventory (ELALI) and the Affective Disposition Scale (ADS). 78 in-service teachers and 132 pre-service teachers participated in the study. The findings revealed differences between in-service and pre-service teachers’ responses to the ELALI, yet overall both groups demonstrated deficiencies. The results of the ADS showed that both groups had a similar perception of language assessment. The analysis of the data obtained helped to identify that, although in-service and pre-service teachers have a weak understanding of English language assessments, they regard assessment positively and focus on students’ learning process rather than the grading of a final product.Assessment is an essential tool to measure students’ progress. It is paramount for teachers to understand their classroom assessment practices to make informed educational decisions. This study seeks to identify in-service and pre-service teachers’ understanding of knowledge and affective dispositions towards language assessment through two instruments: theEnglish Language Assessment Literacy Inventory (ELALI) and the Affective Disposition Scale (ADS). 78 in-service teachers and 132 pre-service teachers participated in the study. The findings revealed differences between in-service and pre-service teachers’ responses to the ELALI, yet overall both groups demonstrated deficiencies. The results of the ADS showed that both groups had a similar perception of language assessment. The analysis of the data obtained helped to identify that, although in-service and pre-service teachers have a weak understanding of English language assessments, they regard assessment positively and focus on students’ learning process rather than the grading of a final product.