Spirulina platensis extracts have exhibited considerable anti-cancer effects. To investigate the efficacy of the Spirulina extract enriched for Braun-type lipoprotein (Immulina®) for breast cancer treatment, 4T1 breast tumor-bearing mice were treated with 40 mg/kg Immulina® daily and the tumors' growth and metastasis were assessed. Also, CD4, CD8, and CD56 staining were performed to investigate the Immulina® effect on the immune cells' recruitment to the tumors by immunohistochemistry. Immulina® could significantly (P < 0.001) inhibit 4T1 breast tumors' growth. Immulina®-treated group exhibited a 63% decrease in the tumors' volume in comparison with control (P < 0.001). Also, Immulina® could significantly (P < 0.001) decrease metastatic burden at the vital organs as 68% and 61% decrease in the liver and lungs metastatic colonies were observed, respectively. Also, Immulina® could increase mean survival time of the tumor-bearing mice for 29 days. The Spirulina-treated mice tumors contained significantly more infiltrated NK, CD4+, and CD8+ T lymphocytes in comparison with control. Taking together, Immulina® can be a safe anti-cancer supplement with the ability to cause direct apoptosis to the cancer cells and activate the immune system against tumor. This supplement with natural origin seems to have bright future to help breast cancer patients. © 2019 John Wiley & Sons, Ltd.