Background: Osteosarcoma (OS) is the most prevalent bone-related malignancy with a high mortality rate among children and adolescents. In the present study, first we explored the effects of astaxanthin (AST) on proliferation and differentiation of the MG-63 osteosarcoma cell line, and then compared its effects with AhR endogenous ligand (FICZ).Methods: Cell proliferation and cytotoxicity assay were performed using MTT. To identify possible mechanisms underlying AST-induced changes in osteogenic metabolism via the AHR pathway, we defined changes in CYP1A1, osteocalcin, osteopontin, type I collagen, and Runx2 gene expression using RT-PCR.Results: AST upregulated CYP1A1, osteocalcin, osteopontin, type I collagen, and Runx2 expression in trends of increasing its concentration. FICZ showed a biphasic effect on MG-63 cell proliferation. At high concentrations, it significantly decreased the cell viability, while at lower concentrations it was increased as compared to the control. Increasing FICZ concentrations from 1 nm to 1 μM, down-regulated the expression of Runx2, osteopontin, osteocalcin and collagen type 1 at the transcriptional levels. It seems that AST can augment the proliferation and differentiation of MG-63 via the AhR-dependent pathway, while FICZ suppresses the proliferation and differentiation of MG-63.Conclusion: We concluded that various AhR ligands show different behaviors in the modulation of MG-63 cells.