Factor XIII (FXIII) deficiency is a rare, inherited or acquired coagulation disorder that potentially precipitates fatal haemorrhage. We report two consecutive pediatric patients with Henoch-Schönlein purpura (HSP) and symptomatic decrease in FXIII. The possible FXIII deficiency should be kept in mind by every doctor taking care of patients with HSP, in spite of normal value of routine coagulation tests.