Ultralight metamaterials with negative Poisson's ratio have garnered widespread attention in engineering and research disciplines, thanks to their exceptional energy absorption capabilities. With the rapid advancement of additive technologies, the relevance of these materials has further intensified. They are in high demand across diverse industries, including aerospace, biomedicine, civil and mechanical engineering, the military, automotive, sports, and electronic devices. The purpose of this paper is to present a new modified 3D arc-star-shaped structure with a negative Poisson's ratio based on the modified 2D arc-star-shaped structure. Poisson's ratio values were analyzed using the Finite Element Method with the ANSYS software package. Results show that for certain geometric parameters, the modified 3D arc-star-shaped structure exhibits negative Poisson's ratio values. Besides, comprehensive investigations were conducted to understand the mechanical properties of the modified structure, particularly focusing on the Young's modulus. Overall, this study contributes to the development of ultralight materials with unique mechanical behavior and potential applications in different fields.