Based on continuous waveform, surface wave and body wave data from teleseismic events recorded by broadband seismic network stations in the southeastern margin of the Tibetan Plateau, we retrieved 6–120 s Rayleigh wave phase velocity and 6–50 s group velocity dispersion curves for station pairs, as well as receiver functions beneath all of the stations. The Rayleigh wave phase velocity dispersions at overlapping periods based on ambient noise empirical Green's functions were found to be congruent with those based on teleseismic surface wave data. We then performed inversion to obtain a reliable 3-D shear wave velocity structure by using both the surface wave dispersion measurements and receiver functions. The resulting shear wave velocity distribution revealed that low-velocity zones (LVZs) are ubiquitous in the mid-lower crust beneath the Chuandian block, the Songpan-Ganze fold belt, and some parts of the western Yangtze platform. This result differs from those of previous studies, which indicated that LVZs are mainly concentrated in the lower crust beneath the Chuandian block. We also found that the LVZs vary substantially in terms of occurrence depth, thickness, and anomaly strength. They are also influenced by the major fault zones, especially the Lijiang-Xiaojinhe fault, and the tectonic blocks in the study area. Extremely high Poisson's ratios (σ > 0.3) and low shear wave velocities (Vs < 3.4 km s–1) coincide in the northwestern margin of the Chuandian block and the region to the south of the Sichuan basin, indicating the existence of partial melt in the mid-lower crust in that area. The mantle LVZs exhibit spatial consistency with crustal LVZs to some degree in the eastern Songpan-Ganze fold belt, Shangrila sub-block, and Yajiang sub-block, implying the existence of a weak and low-density layer in the upper-most mantle.