The authors present mesoscopic thermal transport measurements of individual multiwalled carbon nanotubes (MWNTs) using a microfabricated suspended device. The thermal conductivity of a single MWNT is found to be over 3000 W/m K at room temperature, significantly higher than previous bulk measurements. The temperature dependence of the thermal conductivity exhibits a peak at 320 K due to Umklapp phonon scattering. The thermoelectric power shows a linear temperature dependence with a value of 80 μV/K at room temperature. The study highlights the importance of mesoscopic measurements for understanding the intrinsic thermal properties of single nanotubes, which are often dominated by tube-tube junctions in bulk samples. The experimental techniques used can be applied to other nanoscale materials to study their thermal properties.The authors present mesoscopic thermal transport measurements of individual multiwalled carbon nanotubes (MWNTs) using a microfabricated suspended device. The thermal conductivity of a single MWNT is found to be over 3000 W/m K at room temperature, significantly higher than previous bulk measurements. The temperature dependence of the thermal conductivity exhibits a peak at 320 K due to Umklapp phonon scattering. The thermoelectric power shows a linear temperature dependence with a value of 80 μV/K at room temperature. The study highlights the importance of mesoscopic measurements for understanding the intrinsic thermal properties of single nanotubes, which are often dominated by tube-tube junctions in bulk samples. The experimental techniques used can be applied to other nanoscale materials to study their thermal properties.