Purpose: Primary subclavian venous thrombosis is an uncommon condition that usually affects young and active people. Anticoagulation alone without addressing the underlying pathology may result in post-thrombotic syndrome (PTS) in 40-50% of patients. Decompression with a first rib resection and an endovenous treatment to restore vein patency is recommended to prevent PTS. While the treatment is safer, there is little published data on functional and patient-reported outcomes in this group. Methodology: Patients between February 2020 to May 2026 presenting with primary subclavian venous thrombosis were recruited prospectively. Patients completed the DASH questionnaire and a validated thoracic outlet syndrome survey. All patients had the first rib removed via an infraclavicular incision with an endovascular venous procedure to address the thrombosis. The primary outcome was patient-reported symptoms using validated tools, and the secondary outcome was the clinical result according to Derkash classification. Results: 19 patients were included and 7 were females. The median (range) age was 27 (16-54). The length of the index presentation hospital stay was 4 days, and there were no returns to theatres. 18 patients had a patent vein during follow-up. There was an overall improvement in the DASH score with a 15.8-point difference. 16 patients reported “good” to "excellent" improvement using the Derkash classification. The thoracic outlet syndrome survey improved in all categories (pain, sports, work, emotions, lifestyle) between two and nine points per domain. Conclusion: Patient reported outcomes following endovenous therapy and first rib resection are good, with improvements observed from baseline. Longer-term functional outcomes require further reporting in this young group of patients.