Terra MODIS has been in operation for more than 6 years since its launch in December 1999. It has been continuously making global observations for scientific studies of the Earth system and its environment and climate changes. MODIS has 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). An on-board blackbody (BB) is used on a scan-by-scan basis for the TEB on-orbit calibration. Another on-board calibrator, a spectro-radiometric calibration assembly (SRCA), is operated periodically for the sensor's spatial and spectral characterization. This paper provides an overview of Terra MODIS TEB calibration algorithms, operational activities and strategies. Results presented include TEB detector noise characterization, functionality, and stability derived using on- orbit observations made from the beginning of the mission to present. Excluding a few noisy detectors, the Terra MODIS TEB performance meets the design requirements, thereby assuring calibration accuracy and science data product quality.