This paper presents the production of mesoporous metals with periodic 3D nanostructures, showing control over the lattice parameter and therefore pore and wire dimensions. The materials have “single diamond” (Fd3m) symmetry and are produced by deposition within a “cubic phase” template of the lipid phytantriol, in a process previously published. The current work shows a mechanism for tuning the nanoscale dimensions of the metal by the addition of a cosurfactant that progressively reduces the lipid bilayer curvature in the template. This swells its lattice parameter and therefore that of the deposited metal. Mesoporous platinum samples were characterized using X-ray scattering, electron microscopy, and electrochemical analysis. The structures exhibit unit cell sizes ranging from 13 to 20 nm, with wire thicknesses from 3.0 to 5.3 nm and estimated pore dimensions from 6.2 to 8.8 nm. The size control in these materials provides a mechanism for control of electrochemical behavior in electrocatalysis and sensors. Furthermore, the use of the templates in other metal and semiconductor materials suggests that size control offers possibilities for metamaterials with designed optoelectronic properties.