The purpose of this study was to evaluate the production design of a novel breast phantom, which has adjustable breast glandular fractions and potential application in the mammography quality assurance/quality control system. The breast phantom was based on a urethane resin that was used to adjust the breast glandular fraction by varying the amount of plasticizer added. The resin was cured at constant temperature and humidity. Theoretical phantom properties, such as elemental composition, specific density, effective atomic number, electron density, and linear attenuation coefficients, at various energies were compared to those of breast tissue tabulated in the ICRU 44. These properties were also compared to polymethyl methacrylate resin and BR12. The novel breast phantom was made to represent breast glandular content calculated from breast tissue of the ICRU 44. We hypothesized that the breast phantom theoretical properties are approximately equal to those of the BR12, which is known for being an excellent substitute breast phantom. It was found that the phantom can be used to improve both mammography performance and dosimetry.