OBJECTIVE: Demonstrate the effectiveness of complex decongestive therapy (CDT) in patients with chronic venous insufficiency (CVI). METHODS: A single-blind randomized controlled trial was conducted, where the participants were patients with CVI (n = 21/42) were assigned randomly to an experimental group (n = 11/22) or a control group (n = 9/18). A treatment of CDT (manual lymphatic drainage, intermittent pneumatic presotherapy, bilayer bandage) was applied to the experimental group for 4 weeks 2 days per week and no treatment was applied to the control group. The patients were evaluated at baseline (t0), 1 week after finishing the intervention (t1), and 6 weeks after the intervention (t2). The effectiveness of the treatment on symptoms and quality of life (QoL) (heaviness, pain and Chronic Venous Insufficiency Quality of Life [CIVIQ-20] questionary), edema, venous flow, and impedanciometry measurements was evaluated. RESULTS: An improvement in the patient's QoL was observed: there was a decrease in symptoms such as heaviness and pain, an increase in the average velocity of the left femoral vein and left internal saphenous vein (ISV), a decrease in the ISV diameter in both extremities and a decrease in body mass index and fat mass in both extremities. These results were maintained when following up at 6 weeks, except for the improvement of QoL. CONCLUSIONS: CDT treatment improves the CIVIQ-20 and Venous Clinical Severity Scores. It also improves symptoms (pain and heaviness), venous flow velocity (superficial veins and deep veins [common femoral vein, femoral vein, popliteal vein]) and decreases body mass index, fat mass, and ISV diameter.