Study abroad (SA) has become widespread. Most international students (Int'l Ss) are assumed to want to improve their target language (TL) skills and other related skills/knowledge by interacting with locals and people from other countries. This is referred to as situated learning (Lave & Wenger, 1991). However, TL-mediated socializing opportunities are not automatically taken for granted (Kinginger, 2009). The presenter investigated how Int'l Ss construct their own TL-mediated socializing opportunities and can grow through socializing as his longitudinal qualitative study. He collected qualitative data from nine Japanese undergraduate students who studied in English-speaking countries for short or long periods before, during, and/or after their SA using multiple research techniques. The main findings show that Int'l Ss lived in dynamically changing social environments and that each research participant developed his/her social networks in three patterns (gradual, click, and thin or loose) and then succeeded in co-constructing his/her TL-mediated affinity spaces (Gee, 2004) in different contexts. He also found that their TL-mediated socializing could be ecologically co-constructed by four categories of factors. Furthermore, he clarified that TL-mediated socializing enabled the students to grow as TL users. The presenter will discuss how to promote Int'l Ss' situated learning through socializing.