With increasing demands of miniaturized optical systems in biomedical applications, a tunable focus lens, which moduluates focal length of a lens actively, has been developed in various methods and types. A tunable liquid-filled lens actuated by pneumatically driven pressure has advantages in a wide tuning range and better optical performance, suitable for miniaturized optical systems. For the last decades, studies have been conducted for antireflection that aims to achieve clear images through maximum light transmittance by incorporating the nanostructures on lenses and various substrates. Antireflection significantly minimizes surface reflectance by reducing the Fresnel reflection at air-membrane interfaces. Especially, antireflective structures (ARS), bioinspired subwavelength structures from the cornea of a butterfly eye, can significantly reduce the Fresnel reflection by controlling geometrical parameters to adjust effective refractive index. A tunable liquid-filled lens can enhance light transmission for decreasing the Fresnel reflection by applying the ARS on a flexible membrane. In this work, a novel tunable liquid-filled lens with the ARS on a flexible membrane is presented. Poly-dimethylsiloxane (PDMS) is used as a flexible membrane bonded to a 2.5 mm PDMS lens chamber. A tunable liquid-filled lens with the ARS membrane is fabricated by using a simple wafer-level N/MEMS fabrication. The proposed tunable liquid-filled lens will provide new approaches for miniaturized biomedical imaging applications.