The development of a SERS substrate with high uniformity and sample-to-sample reproducibility is reported. Nanostructured poly(p-xylylene) films are prepared using an oblique-angle polymerization method, and SERS-active metals are deposited onto the nanostructured polymer by using thermal evaporation (see figure). The use of the substrate for a robust and reagentless detection of both Gram-positive and Gram-negative bacteria is demonstrated.