Three-dimensional (3D) cancer cell models, such as 3D multicellular spheroids, are superior models of in vivo systems than the more popular two-dimensional (2D) cell culture. 3D cancer spheroids provide a closer reflection of tumor gene expression and biology than 2D cultures. This is particularly relevant for drug development and precision medicine programs were cell culture conditions that better reflect the 3D tumor environments, including matrix stiffness, would be highly advantageous. A key challenge for the routine application of embedded 3D cancer spheroids in precision and drug programs is the lack of high throughput and uniform production of spheroids in a biocompatible matrix. To address this, we have developed a high-throughput method of producing 3D multicellular cancer spheroids embedded inside a tissue-like matrix using a custom-built drop-on-demand 3D bioprinter for the first time. The 3D bioprinter is capable of printing a cell-suspension ink with up to 300 million cells/mL and a cell viability greater than 95%. We have validated the 3D bioprinting using glioblastoma, neuroblastoma and lung cancer cells. The 3D bioprinted spheroids were confirmed to maintain all the biological characteristics typically found in a cancer spheroid. In particular, the 3D bioprinted cancer spheroids were shown to be viable and proliferating, preserved the apoptotic and cancer-stemness characteristics and using super-resolution lattice-light sheet microscopy, we showed the spheroids maintained the same structural integrity as manually formed spheroids. The potential application of the 3D bioprinted spheroids for high-throughput drug screening in 3D environments was demonstrated using doxorubicin as the model drug. 3D-bioprinting of patient-derived cancer cells for precision medicine applications is now underway. High-throughput embedded 3D bioprinting has enormous potential to accelerate precision medicine, drug discovery and cancer biology.