An emerging field of nanoparticle-mediated cancer therapy is based on the interaction of nanoparticles with radiofrequency (RF) energy to induce hyperthermia or thermal cytotoxicity within cancer cells. In this work, the heating properties of ultra-short single-walled carbon nanotubes (US-tubes) and gadonanotubes (GNTs) were assessed in an external radiofrequency field (900 W, 13.56 MHz). Surfactant (Pluronic F-108) suspensions of US-tubes (carbon-based nanocapsules that are 20-80 nm in length and 1.4 nm in diameter) and GNTs (US-tubes loaded internally with Gd3+ ions) heated in a concentration dependent manner when the RF field was applied. The observed bulk heating of the sample suspensions have been attributed to the nanomaterial itself and not the background surfactant solution. The efficacy of these remotely triggered heating agents to produce thermal cytotoxicity was then investigated in vitro in three different hepatocellular cancer cell lines (Hep3B, HepG2, and Snu449). In all cases, cancer cells that were treated with either US-tubes or GNTs in conjunction with RF had lower viabilities than those treated with RF alone. The ability of GNTs to induce thermal cytotoxicity in vivo was then investigated using subcutaneous tumor models in nude mice. Histopathological analysis of treated tumors demonstrated more pronounced and widespread cell damage in tumors treated with GNTs and RF than in the control tumors. It is anticipated that these results will aid in the future development of nanoparticle-mediated cancer therapy by hyperthermia.