Objective: To investigate the effects of exosomes derived from tumor-associated macrophages (TAMs) on migration and invasion of MDA-MB-231 cells in triple negative breast cancer. Methods: The MDA-MB-231 cells, a human breast cancer cell line, were divided into the experimental group and the blank control group. The exosomes were isolated from the supernatant of human peripheral blood mononuclear cells (THP-1) by a multi-step ultracentrifugal procedure. The effects of exosomes on migration and invasion of MDA-MB-231 cells were studied by endocytosis assay of exosomes, Transwell migration assay and Celigo scratch assay. Results: Exosomes were ingested and endocytosed by MDA-MB-231 cells, brought into the cytoplasm at 3h and enriched significantly at 6h. Compared with the blank control group, the number of metastatic cells in the Transwell compartment (241±3.35) and its variation relative to normal cells (144±2.33) in the experimental group were significantly increased (P<0.05). The 24 h migration rate of MDA-MB-231 cells treated with exosomes in the scratch assay showed similar results (39.86±3.47 in the experimental group vs. 24.48±2.97 in the control group, P<0.05). Conclusion: TAM-derived exosomes can be ingested and endocytosed by MDA-MB-231 cells, and promote their migration and invasion in vitro.