We report a now 13-year-old male with trisomy 21, hypothyroidism, and insulin-dependent diabetes who developed acute hemiplegia due to the antiphospholipid antibody syndrome (APS) at age four. The risks of long-term anticoagulation were initially considered to be high; hence, he was treated with monthly infusions of intravenous immunoglobulin (IVIG) at 2 g/kg for 2 years and then every other month for 7 years. Antiphospholipid antibodies were no longer detectable within 6 months and have continued to be negative. There was no clinical deterioration or further changes on magnetic resonance arteriography over 7 years. IVIG may be an alternative therapeutic choice for children with APS who are not candidates for conventional anticoagulation.