Gold nanorod-mediated photothermal therapy has been widely explored for cancer treatment. However, timely evaluation of the therapeutic response is difficult as current diagnostic approaches are largely based on measurements of tumor volume. The present study developed a non-invasive imaging strategy to rapidly assess the efficacy of photothermal therapy in mice bearing human tumor xenografts. In this study, gold nanorods modified with carboxylated bovine serum albumin showed both anti-tumor and anti-angiogenesis effects under near-infrared laser irradiation. An α(v)β3 integrin-targeted multi-modal nanoprobe, Dendrimer-arginine-glycine-aspartic acid (Den-RGD), was designed and intravenously injected into mice bearing tumor xenografts at 24 h after photothermal therapy. Magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging demonstrated that the Den-RGD not only visualized the tumors with high target-to-background ratio, but also showed the ability to evaluate the therapeutic response by monitoring the tumor neovasculature. Additionally, the target-to-background ratio on MRI and NIRF imaging correlated with the microvessel density in the Den-RGD groups. Immunofluorescence staining confirmed the targeting specificity of Den-RGD to the neovasculature at the tumor periphery. This dual-modal imaging method holds the promise of evaluating therapeutic efficacy in vivo. Nanomedicine provides a multi-functional platform for treatment of cancer and image-guided assessment of anti-cancer therapy.