a b s t r a c t This study demonstrates a simple and efficient strategy for the sensitivity improvement in detection of biomolecules via surface plasmon resonance field enhancement in a Kretschmann configuration. Syner-gistic coupling effects between propagating and localized surface plasmons (SPs) were demonstrated by incorporating arrays of Au nanoparticles (AuNPs) in-between DNA sensing assays. AuNPs with 5 nm or 15 nm diameter were incorporated respectively on the top of the streptavidin layer, and the coupling-induced sensitivity enhancement was systematically investigated. Uniform dispersion of AuNPs was confirmed by TEM analysis. The overall sensing capability of each system was investigated in terms of the reflectivity change, angular shift, and affinity constant for the DNA hybridization process and it was found that AuNP-arrays with appropriate size and lateral distribution led to the best efficiency. The experimental results were in good agreement with numerical simulation data based on a rigorous coupled wave analysis (RCWA).