Background: Youth involved in the U.S. child welfare system (CWS) are at risk for mental health problems, including suicidal ideation (SI). However, the relationship between preteen suicidal ideation and academic outcomes has not been considered. Methods: This study uses data from two nationally representative longitudinal surveys of CWS-involved youth to examine the association between preteen suicidal ideation (ages 7-11) and subsequent academic well-being (ages 12-17) among CWS-involved youth in the United States. Suicidal ideation was assessed using a single self-report item. Academic well-being was assessed through a number of constructs related to young people's ability to thrive in the present and future, including school engagement, academic achievement, and expectations of what their lives would look like in adulthood. Linear regression models with person-level random effects were estimated. Results: Findings indicate CWS-involved youth with a history of preteen suicidal ideation performed worse across all measures of adolescent academic well-being compared to their peers without a history of suicidal ideation. Conclusions: These findings, though associational, have potentially broad implications for understanding how early life suicidal ideation may impede CWS-involved youths' ability to thrive academically.