This chapter presents a systematic review of research on Language Assessment Literacy (LAL) for teachers, focusing on publications from 2010 to 2020, with additional insights from more recent studies published through 2023. It identifies five main themes essential for understanding and improving Teacher Assessment Literacy (TAL): (1) conceptualization of teacher assessment literacy, (2) teacher conceptions of assessment, (3) teacher assessment practice, (4) factors mediating assessment, and (5) assessment training. The discussion underscores these five interrelated areas as essential for improving TAL through reflected practice and targeted training, highlighting the importance of personal and contextual influences on assessment. Practical implications for stakeholders (e.g., teachers, policymakers, and assessment specialists) are also outlined, emphasizing collaboration and continuous professional development as pathways to enhancing TAL and fostering assessment-informed education.