The use of additive manufacturing (AM) is expanding rapidly; however, the mechanical behavior of printing materials has yet to be fully elucidated. In this study, we examined UV-cured photopolymers designed for use in PolyJet systems. We tested the shore hardness and impact characteristics of the photopolymer in accordance with ASTM D2240-15 and ASTM D256-10, respectively. The coefficient of variance among shore hardness measurements was low. We also investigated the influence of stress concentrators fabricated using additive (3D printing) or subtractive (milling) manufacturing methods. Overall, specimens with an AM stress concentrator were approximately 15% stronger than those with a milled stress concentrator. Our results provide a valuable reference pertaining to the mechanical behavior of photopolymers.