Osteosarcoma, which has poor prognosis after metastasis, is the most common type of bone cancer in children and adolescents. Therefore, plant-derived bioactive compounds are being actively developed for cancer therapy. Artemisia apiacea Hance ex Walp. is a traditional medicinal plant native to Eastern Asia, including China, Japan, and Korea. Compound 3-24, derived from A. apiacea, has demonstrated analgesic, anti-inflammatory, antitumour, and immunoregulatory properties; however, there are no published studies on Compound 3-24 isolated from the aerial parts of A. apiacea; thus, this study aimed to evaluate the antitumour activity of Compound 3-24 against human osteosarcoma cells. In the present study, Compound 3-24 (> 99% purity) isolated from A. apiacea induced significant cell death in human osteosarcoma MG63 cells in a dose- and time-dependent manner; cell death was mediated by apoptosis, as evidenced by cleaved-PARP, cleaved-caspase 3, anti-apoptotic proteins (Survivin and Bcl-2), pro-apoptotic proteins (Bax), and cell cycle-related proteins (Cyclin D1, Cdk4, and Cdk6). Additionally, a human phosphokinase array proteome profiler revealed that Compound 3-24 suppressed AKT-dependent downstream kinases. Further, Compound 3-24 reduced the phosphorylation that PRAS40 associated with autophagy and metastasis, induced autophagosome formation, and suppressed programmed cell death and necroptosis. Furthermore, Compound 3-24 induced antimetastatic activity by suppressing migration and invasion of MMP13, which is the primary protease that degrades type I collagen for tumour-induced osteolysis in bone tissues and preferential metastasis sites. Taken together, our results suggest that Compound 3-24 is an attractive target for treating human osteosarcoma.