Marrow niches in osteosarcoma (OS) are a specialized microenvironment that is essential for the maintenance and regulation of OS cells. However, existing animal xenograft models are plagued by variability, complexity, and high cost. Herein, we used a decellularized osteosarcoma extracellular matrix (dOsEM) loaded with extracellular vesicles from human bone marrow-derived stem cells (hBMSC-EVs) and OS cells as a bioink to construct a micro-osteosarcoma (micro-OS) through 3D printing. The micro-OS was further combined with a microfluidic system to develop into an OS-on-a-chip (OOC) with a built-in recirculating perfusion system. The OOC system successfully integrated bone marrow niches, cell‒cell and cell-matrix crosstalk, and circulation, allowing a more accurate representation of OS characteristics . Moreover, the OOC system may serve as a valuable research platform for studying OS biological mechanisms compared with traditional xenograft models and is expected to enable precise and rapid evaluation and consequently more effective and comprehensive treatments for OS.