This study assumes that preventing the risk of social exclusion (RSE) of children, in the context of ECEC, entails guaranteeing ECEC availability and pedagogical practices that provide children with the necessary skills for healthy and successful development. This can be achieved by strengthening the protective factors in the child's surroundings. The overall research goal was to determine the accessibility and describe the quality of attendance of children at risk of social exclusion in the Croatian ECEC system. The sample consisted of 3,500 children from 66 ECEC facilities, or 6% of all children aged 5 to 7 attending ECEC programs at that time, from 10.4% of all the ECEC facilities operating in Croatia. Data were collected through a questionnaire to assess the etiological and phenomenological aspects of RSEs among early years and preschool age children (ECEC teachers' version). The research confirmed that RSEs did influence the children's ECEC attendance. The greatest obstacles to accessibility of ECEC are risk of poverty and minority ethnic identity of children. Inconsistencies in the quality of the Croatian ECEC system are explained as a missed opportunity for the potential of ECEC to prevent RSEs.