Cucurbitacin E (CuE), a potent member of triterpenoid family isolated from plants, has been confirmed as an antitumor agent by inhibiting proliferation, migration, and metastasis in diverse cancer. However, the effects and mechanisms of CuE on osteosarcoma (OS) have not been well understood. This study aimed to test whether CuE could inhibit growth and invasion of OS cells and reveal its underlying molecular mechanism. After various concentrations of CuE treatment, the anti-proliferative effect of CuE was assessed using the cell counting Kit-8 assay. Flow cytometry analysis was employed to measure apoptosis of OS cells. Cell cycle distribution was analyzed by propidium iodide staining. Transwell assay was performed to evaluate the effect of CuE on invasion potential of OS cells. The protein levels were measured by Western Blot. In addition, the potency of CuE on OS cells growth inhibition was assessed in vivo. Our results showed that CuE inhibited cell growth and invasion, induced a cell cycle arrest and triggered apoptosis and modulated the expression of cell growth, cell cycle and cell apoptosis regulators. Moreover, CuE inhibited the PI3K/Akt/mTOR pathway and epithelial-mesenchymal transition (EMT), which suppressed the invasion and metastasis of OS. In addition, we also found that CuE inhibited OS cell growth in vivo. Taken together, our study demonstrated that CuE could inhibit OS tumor growth and invasion through inhibiting the PI3K/Akt/mTOR signaling pathway. Our findings suggest that CuE can be considered to be a promising anticancer agent for OS.