Aim: As retinal microvasculature (RMV) can be assessed non-invasively, it presents an opportunity to examine the health and disease of the human microcirculation, as RMV alterations have been recognised as one of the earliest signs of cardiovascular risk. This review summarises current literature on the associations between physical activity (PA), sedentary behaviour (SB) and/or adiposity and RMV in children and adolescents aged 0-18 years. Methods: Six databases were searched (MEDLINE, Scopus, Web of Science, ScienceDirect, PsycINFO and CINAHL), through to December 11, 2019. English, Portuguese, French, Spanish or Dutch were the languages searched. Meta-analyses were performed using the meta-analyst software. Results: A total of 6796 studies were screened, and 26 studies were included, representing 24 448 participants, from 12 different countries. Studies reporting results on weight status were twenty-three, PA was assessed in six studies, and SB was assessed in three studies. Four studies examined weight status and PA/SB. Meta-analysis was performed for two studies and showed that children with obesity have smaller retinal arterioles (−2.38 µm difference, 95% CI 0.62, 4.15 µm) and larger retinal venules (2.74 µm difference, 95% CI −4.78, −0.72 µm) than children without obesity. Conclusion: Results showed that adiposity was associated with microvascular alterations in children and adolescents. Increased adiposity, lack of PA and high levels of SB were negatively correlated with vessel width parameters.