This article presents an endoscopic 3D printer using the photo-polymerization additive method. The proposed endoscopic principle allows printing 3D objects through a flexible optical image guide. The concept is first to transmit a pattern using ultraviolet light projected through the endoscopic optical system on the printing surface. A layer by layer printing is performed by moving the focusing plane along the z-axis. The endoscopic optical design is based on a Digital Micro-Mirror (DMD) projector, an image guide (a fiber bundle of 70 000 fibers) and optical lenses. It is modeled and simulated using the Zemax optical software. The projected pattern from the DMD is injected into the image guide. Then, the pattern is refocused on the printing surface, which is the transparent bottom of a vat full of resin. First, optical losses and homogeneity of the endoscopic optical system are measured. Then, photopolymer parameters of used resin (Formlab RS-F2-GPWHH-04) are experimentally evaluated. Finally, different multi-layer objects (typically 30 layers) are printed to validate the concept of 3D endoscopic fabrication. Using a 405 nm LED, an optical irradiance of 1.7 mW/cm² on the printing surface is reached. 3D parts are printed with a lateral resolution of 150 μm and a layer thickness of 100 μm on a circular printing surface of 9.54 mm diameter.