Background: The prolonged air leak is probably the most common complication following lung resections. Around 10–20% of the patients who undergo a lung resection will eventually develop a prolonged air leak. The definition of a prolonged air leak varies between an air leak, which is evident after the fifth, seventh or even tenth postoperative day to every air leak that prolongs the hospital stay. However, the postoperative hospital stay following a thoracoscopic lobectomy can be as short as 2 days, making the above definitions sound outdated. The treatment of these air leaks is also very versatile. One of the broadly accepted treatment options is the autologous blood pleurodesis or “blood patch”. The purpose of this trial is to investigate the impact of a prophylactic autologous blood pleurodesis on reducing the duration of the postoperative air leak and therefore prevent the air leak from becoming prolonged. Methods: Patients undergoing an elective thoracoscopic anatomic lung resection for primary lung cancer or metastatic disease will be eligible for recruitment. Patients with an air leak of > 100 ml/min within 6 h prior to the morning round on the second postoperative day will be eligible for inclusion in the study and randomization. Patients will be randomized to either blood pleurodesis or watchful waiting. The primary endpoint is the time to drain removal measured in full days. The trial ends on the seventh postoperative day. Discussion: The early autologous blood pleurodesis could lead to a faster cessation of the air leak and therefore to a faster removal of the drain. A faster removal of the drain would relieve the patient from all the well-known drain-associated complications (longer hospital stay, stronger postoperative pain, risk of drain-associated infection, etc.). From the economical point of view, faster drain removal would reduce the hospital costs as well as the costs associated with the care of a patient with a chest drain in an outpatient setting. Trial registration: German Clinical Trials Register (DRKS) DRKS00030810. 27 December 2022.