This study investigates how primary school English teachers in Malaysia assess word level writing capacity for upper primary students within the Common European Framework of Reference for Languages (CEFR) and how they perceive the appropriateness of students' vocabulary use across CEFR levels A1 to B1. Recognizing vocabulary as a key component of writing ability, particularly in multilingual classrooms, the research addresses the challenge teachers face in applying CEFR lexical descriptors—more specifically lexical range, control, and task-appropriateness—with consistency in classroom assessment. While CEFR has been applied across the nation in Malaysia, prior research has established that the majority of teachers rely on intuition rather than standardized descriptors due to a lack of training, a lack of exemplars, and time constraints. Employing a mixed-methods sequential explanatory design, the research gathered quantitative data from 100 Melaka Tengah district English language teachers using a structured questionnaire, followed by qualitative data from three SJKC Ayer Keroh teachers using semi-structured interviews. Quantitative analysis established trends in CEFR-aligned assessment practice, whereas qualitative findings provided contextual insight into the interpretation and utilization of descriptors by teachers. Results indicate teacher assessment practice variability, with inconsistencies arising from differences in interpretations of vocabulary appropriateness, workload pressures, and learner diversity. While the majority of participants valued CEFR as a guiding framework, the absence of localized rubrics, annotated exemplars, and regular professional development limited its consistent implementation. The study reiterates the need for targeted training modules, collaboratively designed CEFR-based rubrics adapted to Malaysian primary contexts, and inter-rater moderation workshops to determine inter-rater reliability. Such measures can bridge the policy-practice divide to bring more equitable and consistent vocabulary testing and enable students' lexical development in alignment with international standards. The findings contribute to both domestic and foreign studies on CEFR operationalization, vocabulary assessment literacy, and education policy improvement in multilingual primary school settings.