<![CDATA[Diagnostic assessment plays a crucial role in identifying mathematics learning difficulties among elementary school students; however, its implementation continues to face various challenges and has never been synthesized comprehensively. This study aims to systematically review the implementation, diverse instruments, and domains of learning difficulties identified through diagnostic assessment in elementary school mathematics instruction. Following the PRISMA guidelines, a literature search was conducted in the Scopus, Web of Science, and ERIC databases, yielding 25 empirical studies indexed in Scopus for thematic analysis. The findings revealed three main themes. First, the implementation of diagnostic assessment is predominantly conducted at the beginning of instruction with teachers as the main actors; however, its effectiveness is constrained by low assessment literacy and the acceleration of digitalization in the post-pandemic era. Second, the range of instruments includes standardized written tests, error analysis, clinical interviews, performance-based assessment, and adaptive digital platforms, each with their respective strengths and limitations. Third, the identified domains of difficulty include conceptual difficulties with fractions and place value, procedural difficulties associated with mathematics anxiety, and problem-solving difficulties complicated by linguistic barriers. This study concludes that diagnostic assessment needs to be reconceptualized as a multidimensional practice that integrates cognitive, affective, and linguistic aspects. The implications emphasize the importance of enhancing teacher assessment literacy, developing hybrid instruments, and adapting context-sensitive technology to realize differentiated and equitable mathematics instruction in elementary schools.]]>
