Hemodialysis (HD) catheters are prone to thrombotic occlusion. We evaluated tenecteplase, a thrombolytic, for the treatment of dysfunctional HD catheters. Patients with tunneled HD catheters and blood flow rate (BFR) <300 mL/min received open-label tenecteplase (2 mg/lumen) for a 1 h intracatheter dwell. Treatment success was defined as BFR ≥ 300 mL/min and a ≥ 25 mL/min increase from baseline BFR, 30 min before and at the end of HD. Patients without treatment success at the end of the initial visit received another 2 mg dose of tenecteplase for an up to 72 h extended dwell. Of 223 enrolled patients, 34% (95% confidence interval [CI], 28-40%) had treatment success after a 1 h dwell. Mean (standard deviation [SD]) BFR change from baseline was 82 (124) mL/min. Treatment success in those who received extended-dwell tenecteplase (n = 116) was 49% (95% CI, 40-58%), with mean (SD) BFR change from baseline of 117 (140) mL/min. Reported targeted adverse events included five catheter-related bloodstream infections and one thrombosis. No intracranial hemorrhage, major bleeding, embolic events, or catheter-related complications were reported. Tenecteplase administered as a 1 h or 1 h plus extended dwell was associated with improved HD catheter function in the TROPICS 4 trial.