Background: Although there are improvements in breast cancer diagnosis and treatment methods, some breast tumor cells still are resistant to current therapies. Thus, there are attempts all over the world to find an effective way with more toxicity to tumor cells and less to normal cells. In recent years, mesenchymal stem cells (MSCs), due to their native tumor homing property, have been introduced as expression vectors for anticancer proteins, such as TNF-related apoptosis-inducing ligand (TRAIL). However, most tumor cells are resistant to TRAIL or show low sensitivity to it. Thus, it is necessary to find a way to increase the sensitivity of cancer cells and decrease their resistance. One of these ways is combination therapy with herbal drugs. Objectives: This study aimed to investigate the combination of sub-toxic doses of aqueous extract of Berberis vulgaris (AEBV) and MSC-TRAIL on MCF-7 cells as a human breast cancer cell line. Methods: Experiments were set based on in vitro cell culture. Combination therapy was carried out in transwell co-culture plates. The cell viability was determined by the MTT assay. The cell cycle was measured using the Propidium Iodide (PI) staining flow cytometry method. All experiments were performed in triplicate. The data were analyzed by One-way ANOVA test using SPSS software. Results: MCF-7 cells were relatively resistant to MSC-TRAIL and AEBV alone, while a sub-toxic concentration of AEBV (0.5 mg/mL) combined with MSC-TRAIL significantly increased death in MCF-7 cells, showing a synergistic effect.