Social psychological research has increasingly extolled the benefits of intergroup contact as a means of promoting positive relations. However, a growing body of research suggests that formal policies of desegregation are often offset by informal ‘micro-ecological’ practices of (re)-segregation, in everyday life spaces. This paper presents a systematic literature review of recent evidence on this topic (2001-2017), outlining key findings about how, when, where, and why micro-ecological divisions are reproduced. Informal segregation can happen based on ethnicity, religion, socioeconomic status, gender, or gender and ethnicity, despite people being in a shared place. People generally maintain patterns of ingroup isolation as a result of: a) negative attitudes and stereotypes; b) ingroup identification and threat; or c) feelings of anxiety, fear and insecurity. Educational settings have been the main context studied, followed by leisure and recreational places, public urban places and public transport. The paper also identifies three areas of potential future research, highlighting the need to: (1) capitalise on methodological innovations; (2) explore systematically how, when and why the intersectionality of social categories may shape micro-ecological practices of contact and separation; and (3) understand more fully why micro-ecological patterns of segregation are apparently so persistent, as well as how they might be reduced.