Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for the detection and identification of chemical and biomolecular species at trace levels. We developed a highly sensitive surface-enhanced Raman spectroscopy (SERS) based sensor using bimetallic gold-silver nanoparticle arrays. The nanoparticles were fabricated using electroless deposition. The deposition time of AuNPs varied from 10 to 50 s, while AgNPs had a constant deposition time of 30 s. The morphological properties were well correlated to the SERS properties, and we were able to observe the highest SERS activity for AgNPs and AuNPs deposition time of 30 s each using 785 nm laser. Good selectivity and reproducibility were demonstrated for sensing environmental contaminants like rhodamine-6G and methylene blue with an enhancement factor equal to 5 × 107. Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for the detection and identification of chemical and biomolecular species at trace levels. We developed a highly sensitive Surface-enhanced Raman spectroscopy (SERS) based sensor using bimetallic gold-silver nanoparticle arrays. The nanoparticles were fabricated using electroless deposition. The deposition time of AuNPs varied from 10 to 50 s, while AgNPs had a constant deposition time of 30 s. The morphological properties were well correlated to the SERS properties, and we were able to observe the highest SERS activity for AgNPs and AuNPs deposition time of 30 s each using a 785 nm laser. Good selectivity and reproducibility were demonstrated for sensing environmental contaminants like rhodamine-6G and methylene blue with an enhancement factor equal to 5 × 107.