Presented in this paper is a study that examined the status of unmet healthcare needs of children in vulnerable families and identified factors affecting such unmet needs. The Community Child Center (CCC) Child Panel Survey data in Korea were used. A multiple stepwise logistic regression analysis was performed to examine factors influencing unmet healthcare needs of children. Influencing factors comprised predisposing, enabling, and need factors based on the Andersen Behavioral Model of Health Services Utilization. A total of 340 sixth-graders from vulnerable families participated, and 96 (28.2%) children had unmet healthcare needs. Factors included absence of an after-school caregiver (OR = 1.95, 95% CI [1.16, 3.27]), perceived physical symptoms (OR = 1.33, 95% CI [1.02, 1.73]), parental indifference (OR = 1.33, 95% CI [1.002, 1.77]), duration of daily stay at CCCs (OR = 1.32, 95% CI [1.01, 1.71]), and satisfaction with CCC teachers (OR = 0.65, 95% CI [0.49, 0.85]). The relationship with parents and CCC teachers had the strongest influence on unmet healthcare needs of children. In order to reduce the unmet healthcare needs of children in vulnerable families, existing support structures should be expanded to offer financial and administrative support for children’s parents and CCC teachers.