The gyroid pattern, inspired by the natural design found in butterfly wings, combines remarkable strength and flexibility. This study examined sandwich panels using gyroid structures as the core, with outer layers made of carbon fiber-reinforced epoxy. These gyroid cores were produced using a 3D printer with three varying relative densities: 10%, 15%, and 20%. Polylactic acid served as the material for printing the gyroid structures. The printed gyroid cores were then assembled into sandwich panels using epoxy resin between the CFRP laminates. Additionally, polyurethane foam (PUF) was used to fill the cavities of the gyroid cores in another set of samples. Flexural and compression tests were conducted to assess the mechanical properties of the sandwiches. The findings showed that the specific facing stress and core shear strength of the sandwich composites increased with higher sandwich density. The core density was a key factor in determining the flexural properties of the sandwiches. Incorporating PUF improved the deflection at maximum stress and the load sustained after failure. However, the gyroid core sandwiches exhibited higher compression strength, modulus, and energy absorption, as well as better specific properties, compared to the PUF-filled gyroid core sandwiches of the same density.