Dendritic silver nanostructures coated with silica nanofilm are synthesized via hydrothermal etching using silver nitrate, hydrofluoric acid, and hydrogen peroxide and controlling the reagent concentration, reaction time, and temperature. The silver dendritic nanostructures are employed as substrates for surface-enhanced Raman scattering (SERS) and exhibit high sensitivity and excellent stability. Calibration of the Raman peak intensities of rhodamine 6G and thiram allowed quantitative detection of these organic molecules. Our findings are a significant advance in developing robust SERS substrates for fast detection of trace organic contaminants.