OBJECTIVES: The use of mesenchymal stem cells in malignancies has attracted much attention due to their ability to deliver anticancer agents to tumors, including cytokines, chemokines, etc. This study aimed to investigate the effect of MSCs on the neuroblastoma SH-SY5Y cells through proliferation/apoptosis, senescence assessment, telomere length, and telomerase activity in vitro. BAX and BCL2 were also examined as potential signaling pathways in this process. MATERIALS AND METHODS: For this reason, two cell populations (MSCs and SH-SY5Y cells) were co-cultured on trans-well plates for 7 days. In a subsequent step, SH-SY5Y cells were harvested from both control and experimental groups and subjected to flow cytometry, ELISA, real-time PCR, PCR-ELISA TRAP assay, and Western blotting assay for Ki67/Caspase3 investigation, β-Galactosidase assessment, telomere length, and telomerase activity assay. Also, expression of genes and proteins through real-time PCR and Western blotting demonstrated the involvement of the aforementioned signaling pathways in this process. RESULTS: It was found that MSCs contributed significantly to decrease and increase of Ki-67 and Caspase-3, respectively. Also, MSCs dramatically reduced the length of telomere and telomerase activity and increased the β-Galactosidase activity in a significant manner. In addition, significant increase and decrease were also seen in BAX and BCL2 gene and protein expressions, respectively. CONCLUSION: These findings revealed that close interaction between MSCs and neuroblastoma cells causes inhibition of the SH-SY5Y cell proliferation and promotes cell senescence via BAX and caspase-3 cascade pathways.