This study aimed to examine research on out-of-school learning environments in mathematics education from a holistic perspective through a systematic review and to identify prevailing trends. By comparing the general characteristics and methods of studies on out-of-school learning environments in mathematics education conducted at the national level in Türkiye and in the international arena, this study aimed to highlight their similarities and differences. Adhering to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 criteria, 36 studies were included in the analysis. The document analysis method was employed to analyze the selected studies. Within the framework of the analyses carried out, it was determined that qualitative studies were generally preferred, while quantitative and mixed-methods studies were relatively less common. Regarding the temporal distribution of the studies, it was observed that most national-level research was conducted from 2018 onward. When examining the study groups, it was found that both national and international studies primarily focused on middle school students. Furthermore, the findings indicate that existing studies broadly aim to assess the current state of out-of-school learning environments in mathematics education. However, there is a need for more research on designing effective out-of-school learning environments and developing activities to enhance mathematics learning.