Background Mechanochemical ablation is an innovative non-thermal method of treating symptomatic axial superficial venous incompetence. This is a single-centre cohort study aiming to investigate the technical efficacy and clinical effectiveness at one year. Methods Patients with primary, unilateral, symptomatic axial incompetence were offered treatment with mechanochemical ablation using ClariVein® with 1.5% sodium tetradecyl sulphate. Assessments including clinical examination, duplex ultrasound and patient-reported health-related quality of life were performed at baseline and weeks 1, 6, 26 and 52. Results Thirty-two patients were recruited to the study. Complete target vein occlusion at one year was found in 21 (75%) patients. Six patients (21.4%) required secondary procedures, of which three had axial endovenous thermal ablation and three required ambulatory phlebectomy with perforator ligation. There was a significant improvement in the median (interquartile range) Venous Clinical Severity Score from baseline 6 (5–8) to a score of 1 (0–2) at one year (p < 0.001). There was also a significant improvement in health-related quality of life, both generic (p = 0.001) and disease specific (p < 0.001). One patient (3.1%) had a post-procedural non-fatal pulmonary embolus. Conclusions Mechanochemical ablation is a feasible and effective treatment for superficial venous incompetence. When using consensus definitions for anatomical closure, results for mechanochemical ablation may be less favourable than previously reported. Further studies are required to compare clinical and technical outcomes following mechanochemical ablation to other methods of endovenous ablation.