Children with obesity report musculoskeletal pain more than normal-weight children; this may be linked with literature suggesting children with obesity have higher prevalence of pes planus (flatfoot). To further elucidate whether this relation occurs, we conducted a systematic literature review on the co-occurrence of pes planus and paediatric obesity. Empirical articles published until September 2013 were obtained through an electronic search of MEDLINE and SPORTDiscus; included articles examined the association between body weight and pes planus in children. Thirteen cross-sectional studies of varied designs were identified. Methods used to diagnose pes planus varied between studies: imaging modalities, anthropometric measurements and clinical examination. Across all studies, pes planus prevalence among children with obesity ranged widely from 14 to 67%. Nearly all studies indicated increasing pes planus in children with increasing weight. No studies evaluated pain/complications related to pes planus. Our review suggests increased prevalence of pes planus among children with obesity or increasing weight status. Because of differing methodologies, lack of consensus regarding the pes planus definition, the dearth of investigation into pain/complications and the few existing studies, more research is needed to determine a relation between children's body weight, pes planus and associated effects on pain and function.