<p>Description of included articles.</p>

Comparisons involved hearing peers with or without specific learning disorders, and outcomes were based on direct assessments of mathematical abilities or related cognitive processes. A comprehensive literature search was performed in PubMed, Scopus, and Web of Science between March 31 and April 3, 2026, including all studies published up to the search date. In addition, relevant studies were identified through manual screening of reference lists.

Methodological quality was assessed using the Joanna Briggs Institute (JBI) critical appraisal tools. Due to the heterogeneity of the included studies, results were synthesised narratively rather than through meta-analysis.</p> <p>Results</p><p>The twelve included studies showed substantial variability in mathematical performance among DHH individuals. Lower achievement was more consistently observed in tasks with high linguistic demands, such as word problem solving, measurement, and mathematical reasoning, whereas procedural and visually supported tasks were relatively preserved.

Evidence from both preschool and school-aged populations suggests that these differences may emerge early in development and remain observable across different developmental stages. Linguistic proficiency and access to a fully accessible language emerged as key factors associated with mathematical outcomes. Additional sources of variability included educational setting, communication modality, age of language acquisition, and hearing-related characteristics.

Overall methodological quality was generally characterized by moderate methodological concerns, most commonly related to limited control of confounding variables, incomplete reporting of measurement validity, and small sample sizes.</p> <p>Conclusion</p><p>Mathematical difficulties in deaf and hard of hearing (DHH) individuals appear to be domain-specific rather than global and appear to be associated with linguistic access and educational experiences.

Evidence from both preschool and school-aged populations suggests that these differences may emerge early in development and remain evident across studies involving different age groups. These findings highlight the importance of considering language-related factors in both the assessment and instruction of mathematics in DHH learners.</p></div>