It is shown that narrowband one-dimensional photonic crystals can be fabricated from polymeric materials using laboratory scale layer-multiplying coextrusion technology. The tuning of the photonic bandgap is demonstrated with films that selectively filter different regions of the visible electromagnetic spectrum. The layer uniformity of the photonic crystals is evaluated by comparing the measured UV-vis transmission spectra with model simulations, and is independently confirmed with atomic force microscopy. Assemblies of alternating polystyrene and poly(methyl methacrylate) layers exhibit a narrow reflection band with close to 100% reflection in good agreement with the prediction for uniform layers. The flexibility of the process is demonstrated by the fabrication of elastomeric one-dimensional photonic crystals. It is anticipated that this technology will enable the rapid and facile realization of new polymeric optical devices.