Hierarchically flowerlike Ag microstructure with uniform silver nanosheets as building blocks has been facilely prepared on a composite film surface via in situ reduction of Ag+ by a polyaniline component. The morphology of the as-prepared Ag microstructure is determined by the reaction duration, not the concentration of Ag+ in the reaction process. The complex geometry, rough surface, and interlaced nanosheets of the hierarchical Ag microstructure create interstitial sites and thus result in enhanced Raman signals.