(1) Background: Breast cancer-associated lymphedema (BCRL) is a major complication of breast cancer treatment, affects the quality of life of breast cancer survivors who develop it. Manual lymphatic drainage has a beneficial result in combating lymphedema in patients who have undergone breast cancer surgery. The hypothesis consists in complete decongestive therapy reduces the lymphedema at the level of the upper limb on the side of mastectomy. (2) Methods: Twenty-five patients with radical mastectomy and upper limb lymphedema on the mastectomy side were included in this study. Upper limb circumferences were measured with a tape measure at the following levels: metacarpophalangeal joint; distal radioulnar joint; 10 cm distal to lateral epicondyle; 5 cm proximal to elbow joint; 10 cm proximal to lateral epicondyle. (3) Results: Patients received twice weekly manual lymphatic drainage, multi-layer compression bandaging and upper limb muscle stimulation exercises on the mastectomy side twice weekly. The circumference assessed at the level of the metacarpophalangeal joints and distal radio-carpal joint decreased at the final evaluation. Forearm perimetery - 5 and 10 cm distal to the lateral epicondyle the circumference decreased at the final assessment. (4) Conclusions: Patients with breast cancer-related lymphedema should receive comprehensive decongestive therapy in the early stage of lymphedema to achieve rapid clinical results and improved quality of life