Acquired inhibitors to FVIII (anti‐FVIII) are uncommon in children. An acquired anti‐FVIII developed in a previously healthy 4‐year‐old boy treated with penicillin for streptococcal pharyngitis. Aspirin prophylaxis begun for suspected rheumatic fever led to compartment syndromes of all four extremities, which resolved with high‐dose FVIII and surgical decompression. Anti‐FVIII in this patient, and the five additional cases identified in a survey of 160 haemophilia treatment centres, occurred at a median age of 8 years, with median initial and peak titres of 4.6 and 6.9 Bethesda Units (BU), respectively. All six presented with bleeding, including haematomas (three intramuscular, one intracranial), and ecchymoses in three. The median baseline FVIII was 0.05 U mL⁻¹, and the median baseline activated partial thromboplastin time (APTT) was 79.8 s. The inhibitor resolved completely in five patients (83%) within a median 5 months, after treatment with FVIII concentrate, steroids, cytoxan, methotrexate, and no treatment. The inhibitor persisted in the patient with Goodpasture's disease, despite steroids, cytoxan, cyclosporin, and intravenous gamma globulin. Aspirin therapy, in two, worsened ongoing bleeding. The association of penicillin‐like drugs in this and three other cases in the literature suggest that to avoid potential catastrophic bleeding, it is prudent to obtain an APTT prior to initiating aspirin for suspected rheumatic fever. In conclusion, acquired anti‐FVIII inhibitors in children may cause severe bleeding, and remit in the majority after FVIII and/or immunosuppressive therapy.