The reliable detection and monitoring of microRNAs (miRNAs) are of great significance for gaining a better understanding of the functions of miRNAs in a wide range of biological processes. In this work, a competitive DNA microarray-based resonance light scattering (RLS) assay has been developed for the multiplexed detection of miRNAs with relatively high sensitivity and selectivity. After one-step competition hybridization reactions of miRNAs and multiple single strand DNA (ssDNA) conjugated gold nanoparticles (ssDNAsn@GNPs) with immobilized ssDNA probes on the dendrimer-modified slide, the captured ssDNAsn@GNPs are further enlarged through silver deposition. The silver enlarged ssDNAsn@GNPs can generate strong RLS under white light excitation. The simultaneous detection of multiple miRNAs can be easily achieved by monitoring the RLS signal changes of microarrays. In the proof of concept experiment, eight miRNA let-7 family members are detected with high specificity down to 0.2 pM, 0.8 pM, 0.2 pM, 0.2 pM, 0.2 pM, 0.8 pM, 0.8 pM, and 0.8 pM for miRNA let-7a to 7g, and 7i, respectively. Furthermore, the expression levels of eight miRNA let-7 family members in the total RNA extracts from five cell lines have been evaluated, and satisfactory results are obtained.