Complex physical therapy is the main treatment for the secondary lymphedema after breast cancer. The low-level laser therapy (LLLT) has been used in order to stimulate lymphangiogenesis, encourage lymphatic motility, and reduce lymphostatic fibrosis. However, these factors could also favor the development of recurrence and metastasis. The objective of this study is to discuss the use of LLLT in the treatment of lymphedema after breast cancer. This study utilized a systematic review on the use of LLLT in the treatment of lymphedema after breast cancer. Evaluating quality of articles was conducted through the PEDro scale. Of the 41 articles identified, four were considered to be of high methodological quality (score ≥ 5). The low-level laser in the axillary region was performed in all studies. The control group was not similar across studies. The results presented showed that there was a reduction in limb volume in the group subjected to low-power laser when compared with other treatments. No studies have evaluated the risk of metastasis or relapse in the irradiated areas. Because no studies have included the complex physical therapy as the comparison group, we cannot claim that laser treatment is the best efficacy or effectiveness in lymphedema treatment after breast cancer. No studies have evaluated the hypothesis that the LLLT can increase the risk of recurrence or metastasis. Therefore, the questions about the safety of this procedure in cancer patients remain.