Barium strontium titanate (BST) inverse opal photonic crystals (PCs) were fabricated by a process of self-assembly of a polystyrene opal template in combination with infiltration of BST nanoparticles into the voids of a template. In this process, stable monodispersed BST nanoparticles were prepared by dispersing a BST gel into a mixed solvent of 2-methoxyethanol and acetylacetone. Scanning electron microscopy images show that the inverse opals possess a face-centered cubic lattice with a center-to-center distance of the air spheres of 270 nm. The X-ray diffraction result reveals that a ferroelectric perovskite phase was obtained. A photonic bandgap in the visible range is observed from reflection spectra analysis and compared with the theoretical results.