Endovenous radiofrequency ablation (RFA) has been introduced as a less invasive alternative to traditional surgery for varicose veins, but vein thrombosis after RFA remains a concern. This study investigated the influence of endovenous RFA on coagulable states of canine blood, and changes in the vein wall and lumen. Eight canines underwent RFA of the iliac-femoral vein. Levels of plasma granule membrane protein-140, tissue plasminogen activator and plasminogen activator inhibitor-1 increased at different time points after RFA, which were monitored by enzyme-linked immunosorbent assay. Venography after ablation showed that there was left iliac-femoral vein occlusion in three canines and vein stenosis in the remaining five. Histological examination revealed intimal injury and inflammatory cell infiltration of the vessel wall. Our findings suggest that RFA is an effective microinvasive technique, which can result in a hypercoagulable state, with venous thrombosis and stenosis.