Additively manufactured multi-functional metamaterials with low coefficient of thermal expansion (CTE) and programmable Poisson's ratio (PR) were designed and fabricated using Invar 36 alloy via laser powder bed fusion (PBF-LB). The metamaterials exhibit isotropic low CTEs ranging from 1.79 to 1.85 ppm/°C and programmable PR within -0.54 to +0.58. The PR is controlled by the angle θ₁, which governs the transverse deformation behavior. The metamaterials demonstrate superior mechanical performance and a wider operating temperature range compared to polymer-based metamaterials. The design integrates low CTE and programmable PR, enabling applications in temperature-sensitive and mechanical environments. The study confirms the feasibility of using Invar 36 alloy for multi-functional metamaterials, overcoming limitations of traditional manufacturing processes. The results show that the metamaterials achieve isotropic low CTE and programmable PR, with high dimensional accuracy and uniform microstructure. The underlying mechanisms of the PR programmability and the effects of geometric parameters on the material properties were analyzed. The study highlights the potential of these metamaterials for engineering applications, including aerospace, biomedical, and energy systems. The findings demonstrate the effectiveness of the design and manufacturing process, providing a promising alternative for multi-functional integration in harsh environments.Additively manufactured multi-functional metamaterials with low coefficient of thermal expansion (CTE) and programmable Poisson's ratio (PR) were designed and fabricated using Invar 36 alloy via laser powder bed fusion (PBF-LB). The metamaterials exhibit isotropic low CTEs ranging from 1.79 to 1.85 ppm/°C and programmable PR within -0.54 to +0.58. The PR is controlled by the angle θ₁, which governs the transverse deformation behavior. The metamaterials demonstrate superior mechanical performance and a wider operating temperature range compared to polymer-based metamaterials. The design integrates low CTE and programmable PR, enabling applications in temperature-sensitive and mechanical environments. The study confirms the feasibility of using Invar 36 alloy for multi-functional metamaterials, overcoming limitations of traditional manufacturing processes. The results show that the metamaterials achieve isotropic low CTE and programmable PR, with high dimensional accuracy and uniform microstructure. The underlying mechanisms of the PR programmability and the effects of geometric parameters on the material properties were analyzed. The study highlights the potential of these metamaterials for engineering applications, including aerospace, biomedical, and energy systems. The findings demonstrate the effectiveness of the design and manufacturing process, providing a promising alternative for multi-functional integration in harsh environments.