OBJECTIVESChildhood-onset Takayasu's arteritis (cTAK) is a rare disease with high recurrence rates, vascular complications, and mortality. This study aimed to identify the risk factors for poor prognosis in hospitalized patients with cTAK and develop a nomogram prediction model.METHODSThis was a prospective longitudinal multicenter cohort study. Cohorts were categorized into poor and good prognosis groups according to follow-up outcomes. Poor prognosis included vascular complications, disease recurrence, persistent non-remission, and cTAK-related death.RESULTSOf the 111 patients, 73 (65.8%) and 38 (34.2%) were categorized into the good and poor prognosis groups, respectively, with a median follow-up of 36.0 [24.0, 60.0] months. Seven independent factors for poor prognosis of cTAK were identified: the Indian Takayasu Clinical Activity Score with the Acute-Phase Response (ITAS.A), internal carotid artery stenosis, external carotid artery stenosis, aortic insufficiency, mitral insufficiency, tricuspid insufficiency, and hypertensive heart disease (odds ratios: 1.20, 3.21, 3.57, 3.88, 9.08, 15.67, and 7.42, respectively; all P values < 0.05). The nomogram prediction model yielded an area under the receiver operating characteristic curve of 0.79. The C-index of the nomogram constructed based on the prediction model was 0.73. The accuracy of this model was 67.0% after bootstrapping for 1000 repetitions.CONCLUSIONWe used easily accessible clinical and laboratory data to establish a nomogram model for predicting the probability of poor prognosis with hospitalized cTAK patients.