An important unsolved challenge in tissue engineering has been the inability to replicate the geometry and function of vascular networks and blood vessels. Here, we engineer a user-defined 3D microfluidic vascular channel using 3D printing-enabled hydrogel casting. First, a hollow L-shaped channel is developed using a template casting process. In this process, murine 10T1/2 cells are encapsulated within gelatin methacrylate (GelMA) hydrogel using UV photocrosslinking, and upon removal of the template results in a hollow channel within GelMA. Second, human umbilical vein endothelial cells (HUVECs) were cultured within the channel and immunostaining was used to visualize endothelial monolayers. Third, diffusion/permeability studies on endothelialized channels were carried out to demonstrate the barrier function of HUVEC monolayer. Taken together, we develop a facile, cytocompatible and rapid approach to engineer a user-defined multicellular vascular chip that could be potentially useful in developing new vascular model systems.