Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity with persistently positive antiphospholipid antibodies (aPL). Patients with aPL may also experience thrombocytopenia, cardiac valve disease, nephropathy, skin ulcer, or cognitive dysfunction, which are collectively known as non-criteria manifestations of APS. A description is provided of two primary APS patients who received belimumab (10 mg/kg) for an aPL-related manifestation.