Hierarchical self-assembled 3-D ternary Zn2GeO4 nanorods have been successfully synthesized using a simple hydrothermal method. They are formed by two basic parts: a 3-D crystal base and 1-D nanorods nucleated from this base. Mechanisms of this micro/nanostructure growth are suggested to be governed by the change of concentration of ammonia and the reaction time during the self-assembly process. Good crystal lattice quality and morphology were demonstrated by XRD, SEM and TEM analyses. The micro/nanostructures are expected to be promoted in construction of micro/nano-optoelectronic devices.