AbstractObjectivesWe aim to analyze the predictive value of thromboelastography on bleeding severity of patients with chimeric antigen receptor (CAR)‐T cell therapy.MethodsA total of 80 patients with refractory/relapsed hematological malignancy were enrolled and divided into two groups: the severe bleeding group and the non‐severe bleeding group. The thromboelastography data was collected on the day of CAR‐T infusion and the 3rd, 7th, 10th, 13th, 17th, and 20th day after CAR‐T cell infusion.ResultsThe patients of the severe bleeding group had lower platelet (p < .007), maximum amplitude (p = .002), coagulation index (p = .005), and longer coagulation time (p = .019). Increasing trend in reaction time and coagulation time and decreasing trend in Alpha, maximum amplitude, and coagulation index on Days 0–10, opposite on Days 10–20. Univariate logistic regression analysis and multivariable logistic regression analysis showed maximum amplitude on the 3rd day after CAR‐T cell infusion (MA3) (OR = 0.9; 95% CI = 0.84–0.95; p < .001) and cytokine release syndrome grade (OR = 2.57; 95% CI = 1.35–5.32; p = .006) were significantly associated with high bleeding severity.ConclusionsThromboelastography was considered to be a good predictor of bleeding severity.