Previous research has suggested that children and adolescents in residential care are at high risk of suicide. Empirical studies on this topic in South Korea, however, are scarce. Our objectives were to 1) examine the relative risk of suicide among children in residential care compared with those not in residential care, 2) evaluate how the relative risk of suicide is associated with age, and 3) explore the trend in relative risk of suicide over time. We used repeated cross-sectional survey data from nationally representative samples of 848,451 children aged 12 to 18 in South Korea between 2007 and 2018 to examine the association between residence type and risk of suicide. The results of the pooled logistic regression suggest that the suicide risk of children and adolescents in residential care is significantly higher than that of children and adolescents not in residential care. We also found that the association between the type of residence (residential care or not) and risk of suicide among children and adolescents varied depending on their age. We then performed a series of logistic regressions for each survey year to compare the odds ratios of suicide risk in children and adolescents in residential care versus those not in residential care. The findings suggest that the relative risk of suicide among children and adolescents in residential care has increased during the past 12 years. This increasing trend was more prominent in older adolescents.