Multifunctional nanomaterials with targeted imaging and chemotherapy have high demand with great challenge. Herein, we rationally aimed to design multifunctional drug delivery systems by RGD-modified chitosan (CH)-coated nanoneedles (NDs) of gadolinium arsenate (RGD-CH-Gd-AsNDs). These NDs have multifunctionality for imaging and targeted therapy. NDs on intravenous administration demonstrated significant accumulation of As ions/species in tumor tissues, which was monitored by the change in T 1 -weighted magnetic resonance (MR) imaging. Moreover, NDs were well opsonized in cells with high specificity, subsequently inducing apoptosis to the HepG2 cells. Consequent to this, the in vivo results demonstrated biosafety, enhanced tumor targeting, and tumor regression in a subcutaneously transplanted xenograft model in nude mice. These RGD-CH-Gd-AsNDs have great potential, and we anticipate that they could serve as a novel platform for real-time T 1weighted MR diagnosis and chemotherapy. KEYWORDS: chitosan-coated nanoneedles of gadolinium arsenate (CH-Gd-AsNDs), arginylglycylaspartic acid (Arg-Gly-Asp or RGD) peptide-conjugated CH-Gd-AsNDs, magnetic resonance imaging, α v β 3 integrin receptor, tumor imaging, cancer therapy