Three-dimensional (3D) electronic nanomaterials are less explored than their counterparts in the lower dimensions because of the limited techniques for the preparation of high-quality materials. Here we report characterization of and quantum transport measurement on 3D metalattices of Pt grown in the voids of self-assembled templates of silica nanospheres by confined chemical fluid deposition. These Pt metalattices featuring an unprecedentedly large surface area to volume ratio were found to show positive magnetoresistance (MR) at low temperatures, changing from positive to negative in low magnetic fields within a narrow temperature window as the temperature was raised. The low-field MR was attributed to the effect of quantum interference of electronic waves in the diffusive regime in three dimensions, processes known as weak localization and antilocalization. We argue that the presence of the large surface area to volume ratio results in such a strong enhancement in the electron-phonon scatterings that a change in the sign in the MR is enabled.