The imaging of tumor-related multitarget molecules is of great significance to raise the diagnostic accuracy for malignant tumors. Poly(ADP-ribose) polymerase-1 (PARP-1) has emerged as a potential clinical biomarker for tumor diagnosis due to its specific overexpression in cancer cells. High levels of H2O2 in the tumor microenvironment play vital roles in driving cancer progression. Inspired by these achievements, we employed a silver-coated gold nanorod (Au@Ag NR) as a plasmonic probe for dual imaging of intracellular PARP-1 and H2O2 under a dark-field microscope (DFM). Au@Ag NR was used not only to distinguish tumor cells from normal cells but also to induce the apoptosis of cancer cells owing to the etching of Ag shell by H2O2, accompanied by the color change from green to orange. On the other hand, Au@Ag NRs modified with active double-stranded DNA (dsDNA) could be utilized to image PARP-1 in cancer cells and quantitatively detect PARP-1 in vitro by naked eyes or DFM. The reason is that PARP-1 polymerized nicotinamideadenine dinucleotide (NAD+) into large and hyperbranched poly(ADP-ribose) polymer (PAR) on the surface of Au@Ag NRs, preventing the Ag shell from being etched by H2O2. As the PARP-1 activity increased, a blue-shift of the adsorption peak occurred along with a color change from pale pink to green, which could be recognized by naked eyes. Under DFM, its scattering light varied obviously from red to green. The proposed dual-imaging strategy holds good prospects in cancer diagnosis.