<p>First language (L1) attrition has received an increasing amount of interest in applied linguistics, especially with respect to heritage speakers in diasporas. Nonetheless, the literature on Arab heritage speakers is sparse. This paper is a systematic literature review of predictors of Arabic first language attrition in Arab diaspora populations. After adhering to the systematic review procedure, 22 peer-reviewed articles between 2019 and 2024 were located after searching Scopus, Web of Science, and other academic databases. After screening, quality appraisal, and data extraction, the studies were synthesized using thematic analysis. The findings revealed five primary themes and 24 sub-themes that include linguistic, social, educational, and contextual factors related to L1 attrition. According to the findings, the lower levels of exposure to the Arabic language, predominance of the majority language, language practices in the family, educational environments, and language attitudes are central factors in determining the level of attrition. The review also mentions that there is a significant methodological variation among studies, and future research should be more rigorous and comparable.</p>