A practical and feasible bottom-up chemistry approach is demonstrated to dramatically enhance thermoelectric properties of the Bi2Te3 matrix by means of exotically introducing silver nanoparticles (AgNPs) for constructing thermoelectric composites with the hierarchical two-phased heterostructure. By regulating the content of AgNPs and fine-tuning the architecture of nanostructured thermoelectric materials, more heat-carrying phonons covering the broad phonon mean free path distribution range can be scattered. The results show that the uniformly dispersed AgNPs not only effectively suppress the growth of Bi2Te3 grains, but also introduce nanoscale precipitates and form new interfaces with the Bi2Te3 matrix, resulting in a hierarchical two-phased heterostructure, which causes intense scattering of phonons with multiscale mean free paths, and therefore significantly reduce the lattice thermal conductivity. Meanwhile, the improved power factor is maintained due to low-energy electron filtering and excellent electrical transport property of Ag itself. Consequently, the maximum ZT is amazingly found to be enhanced by 304% arising from the hierarchical heterostructure when the AgNPs content reaches 2.0 vol%. This study offers an easily scalable and low-cost route to construct a wide range of multiscale hierarchically heterostructured bulk composites with significant enhancement of thermoelectric performance.