Herein, scientists of TIPC report for the first time a simple and reliable one-pot methodology for the facile synthesis of the Ag/Au–Fe₃O₄ composite NPs. The as-prepared Ag/Au–Fe₃O₄ composite NPs have good crystallinity and saturation magnetization (38.021 emu g⁻¹), resulting in their magnetic recycling. They have good catalytic activity and stability during the reduction of 4-nitrophenol in the presence of NaBH₄. These Ag/Au–Fe₃O₄ composite NPs also have good antibacterial effect for Escherichia coli O1634. Excellent SERS was also shown for the detection of 2-nitroaniline using these Ag/Au–Fe₃O₄ composite NPs. The nanostructure makes the Ag/Au–Fe₃O₄ composite NPs stable and has a high-enhancement effect for Raman detection.