Youth who enter foster care are at risk of mental health need, but questions arise as to the validity of their self-reported symptomatology. This study examines the screening validity of the youth-report version of the Pediatric Symptom Checklist-17 (PSC-17) in a child welfare population. Data come from 2389 youth who completed a version of the PSC-17 adapted for youth report, and their biological and foster parents who completed the parent-report version. Youth also completed a shortened version of the Screen for Child Anxiety Related Disorders (SCARED). Convergent and discriminant validity of the PSC-17 was assessed using multi-trait multi-method matrices. The PSC-17’s internalizing subscale was strongly correlated, attention subscale was moderately correlated, and externalizing subscale was weakly correlated with the SCARED’s anxiety and PTSD subscales. Comparing youth and foster parent scores, the PSC-17 had moderate convergent validity and weak/fair discriminant validity. Comparing youth, foster parent, and biological parent scores, the PSC-17 had moderate convergent validity and weak/fair discriminant validity. The current study provides some support for the validity of the PSC-17 for the population of youth in foster care.