Objective The purpose of this study was to evaluate the radiopacity of 4 commercially available fiber posts. Methods Three commercially available fiber post systems: RelyX? Fiber Post(RelyX), PARAPOST? FIBER LUX(Parapost), and D.T. Light-Post Illusion X-RO(DT) with a new fiber post Macro-Lock Illusion X-RO(ML) were selected. After endodontic treatment of 20 extracted premolars, the teeth were randomly divided into 4 groups. Then the root canal was prepared using the specific drills according to the manufactures’ instructions. The 4 groups of fiber posts were bonded to the root substrate using the Parabond and luting cement ParaCore. Five cylindrical specimens 2 mm thick were cut from each of 4 groups of fiber posts. Radiographic images of all the specimens along with a standard aluminum step wedge were obtained on an occlusal film. Radiodensity levels were subsequently calculated as equivalents of aluminum thickness. The visual examination of the cross-sectional post surfaces were performed with a scanning electron microscope. Results The new fiber post ML group showed greater radiopacity than other 3 groups, followed by RelyX and DT group. However, the Parapost group demonstrated the lowest optical density. Conclusion Radiopacity of the new ML quartz fiber post is greater than those of the other fiber posts selected.