PurposeIt has been proven that fibrinogen deposition exists in IgA nephropathy (IgAN), but its clinical significance has not been identified. We aim to investigate the clinical implication of fibrinogen deposition in evaluating the activity and prognosis of IgA nephropathy.MethodsIn this cohort, 935 adult IgAN patients were divided into 3 groups according to the intensity of glomerular fibrinogen deposition. Primary outcome refers to a composite event of either a ≥ 50% reduction in eGFR or ESRD (eGFR < 15 ml/min/1.73m2, dialysis, or renal transplantation). Factors associated with fibrinogen deposition and prognosis were identified.ResultsThe results showed that the intensity of fibrinogen deposition was positively correlated with eGFR (P< 0.001), serum albumin (P= 0.041), and hemoglobin levels (P< 0.05), but negatively correlated with age (P= 0.04), serum fibrinogen levels (P< 0.001), serum C4 (P= 0.023), the proportion of patients with hypertension (P= 0.003), and the percentage of glomeruli sclerosis (P< 0.001). The prognostic analyses identified that fibrinogen deposition was an independent predictor for the progression of IgAN (P= 0.033).ConclusionOur study indicated that the deposition of renal fibrinogen can predict the prognosis of IgAN with high reliability.