BACKGROUND: Low-density lipoprotein cholesterol (LDL-C) level and lipoprotein(a) [Lp(a)] ≥ 50 mg/dL predict atherosclerotic cardiovascular disease (ASCVD) risk in adults with familial hypercholesterolemia (FH), but their role for children with FH is less clear. OBJECTIVE: This study examined the relationship between elevated Lp(a) and LDL-C levels in a pediatric population with FH and onset of ASCVD in family members. METHODS: Retrospective review of pediatric patients with FH identified LDL-C, Lp(a), and family history of ASCVD. Logistic regression modeling evaluated the association between the child's Lp(a) and peak LDL-C level with earliest age of ASCVD onset in their family. RESULTS: One hundred twenty-nine children from 109 families were identified. Children from families with early-onset ASCVD were 3 times more likely to have high Lp(a) than those with a family history of late-onset ASCVD (OR: 3.77, 95% CI: 1.16-12.25, P = .027) but were not more likely to have highly elevated peak LDL-C (≥190 mg/dL) (OR: 0.45, 95% CI: 0.11-1.80, P = .26). CONCLUSION: Children with FH and family history of early-onset ASCVD were more likely to have Lp(a) ≥50 mg/dL than children with FH and family history of late-onset ASCVD. Family history of early-onset ASCVD was more predictive of a child's Lp(a) level than of a child's peak LDL-C. Measurement of Lp(a) in children with FH may better characterize their cardiovascular risk, particularly when knowledge of family history is limited. Lp(a) testing may also identify children with FH that could benefit from more aggressive management to reduce ASCVD risk.