The Multiangle Imaging SpectroRadiometer (MISR) aerosol optical depths (AODs) over the Tibetan Plateau (TP) are compared with ground-based remote sensing data. The result shows that 27 out of 32 MISR AODs fall within the expected uncertainty, i.e., 0.05 or 20% × AOD. The mean bias and the root mean square error between ground and satellite AODs are 0.01 and 0.03, respectively. The 7-year MISR AOD data are used to study seasonal and inter-annual variations of AOD over the TP. The results show distinct seasonal variation, with seasonal AOD being 0.27, 0.25, 0.13 and 0.11 from spring to winter. AOD over the TP is closely related to that over the Taklimakan desert in summer; however poor correlation is observed in spring. Higher AOD in spring and summer over the TP merits further study, including its causes and implications for climate and environment.