Due to their unique physical and chemical properties, carbon nanotubes have a number of applications in biomedical field as agents for photothermal therapy, drug transport vehicles and biological imaging agents. Single-walled carbon nanotubes (SWCNTs) provide a large platform for the transport of multiple drugs and target agents, while protecting human body from adverse effects of the drugs. SWCNTs also simultaneously serve as biological imaging agents via their intrinsic fluorescence in the near-infrared, where biological tissue is more transparent. In our work, SWCNTs were employed to successfully deliver several siRNA payloads in vitro and in vivo for the purposes of cancer therapeutics. They protected siRNA, non-covalently bound to SWCNT platform, from degradation in blood and facilitated successful transfection via enhanced cellular membrane penetration. Delivery pathways of siRNA were monitored through fluorescence imaging, verifying that SWCNTs could effectively deliver their payload in cancer cells and tumor tissues. SWCNT fluorescence spectroscopy allowed for quantitative assessment of their pharmacokinetics in blood and tissue biodistribution in animal models with human tumor xenografts. As a result, an apparent antitumor activity of siRNA/SWCNT complexes was observed, complimented by the evidence of SWCNT accumulation in tumor. This data suggests that carbon nanotubes can effectively serve as multimodal agents for image-guided therapy in biomedical applications. Due to the specificity of nanotube emission, SWCNTs also show a strong potential for simultaneous delivery and imaging of multiple biological agents at once.