The purpose of this study is to identify the prevalent multilingual pedagogies used in primary education and to map their specific cognitive outcomes between 2015 and 2025. This research is a systematic review of empirical studies published between 2015 and 2025. Major databases, including ERIC, Web of Science, and Scopus, as well as Persian academic databases, were searched. After applying inclusion and exclusion criteria, 60 out of 1,690 identified articles were selected for final analysis. Eligible studies had to focus on the primary education level and report at least one cognitive outcome. The analysis revealed four major categories of pedagogical approaches: (1) Translanguaging-based approaches, (2) Affirming approaches, (3) Scaffolding approaches, and (4) Cross-linguistic approaches. Among them, translanguaging-based pedagogy—appearing in 37 studies, either individually or in combination—was the most prevalent. Furthermore, six categories of cognitive outcomes were identified, with the most frequent being content comprehension (29 studies), followed by literacy development (15 studies). The translanguaging-based approach showed the strongest correlation with content comprehension and language awareness. While 57 studies reported positive results, three studies indicated neutral or negative findings, mainly due to implementation challenges. This systematic review provides robust evidence that multilingual pedagogies are essential tools for students’ cognitive development and should not be viewed merely as socio-emotional support strategies. The findings confirm that employing multilingual approaches can serve as a valuable learning resource in primary education and offer a practical framework for achieving cognitive outcomes.