In vitro engineering of tumor milieus is complex because cancer progression and metastasis involve spatio-temporally evolving cell–matrix interactions, myriad interactions between tumor cells and auxiliary cells, hypoxic cores, leaky unorganized vasculature and a host of signaling molecules. Recent advances in 3D printing approaches enable the precise placement of cells, bioactive factors and biomaterials, thus permitting the recapitulation of several features associated with the in vivo tumor microenvironment. 3D printed in vitro tumor models can serve as robust platforms to study mechanisms of disease progression, enable high throughput screening of drugs and aid the development of next generation molecular therapies. This focused review discusses the importance and relevance of 3D printing technologies in building tumor models in vitro. Several recent 3D printed cancer models are discussed, as also the evolution and features of next-generation models. © 2017 Elsevier Inc.