Well-defined 1D and 3D t-LaVO₄:Ln (Ln = Eu³⁺, Dy³⁺, Sm³⁺) nanocrystals with regular and uniform shapes were synthesized through a simple hydrothermal route assisted by disodium ethylenediaminetetraacetic acid (Na₂EDTA). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), as well as kinetic decay curves were employed to characterize the samples. The results show that the reaction time, pH value of the initial solution, and Na₂EDTA/La³⁺ molar ratio all have an important influence on the dimension and shapes of the final products. By introducing the “splitting mechanism” to the dimension and morphology evolution process from one-dimensional (1D) to three-dimensional (3D) t-LaVO₄ crystals, the nucleation and crystal growth processes were well demonstrated. The Ln³⁺ ions doped t-LaVO₄ samples exhibit respective bright red, blue-white and orange luminescence of Eu³⁺, Dy³⁺, and Sm³⁺ under ultraviolet excitation, and have potential application in the fields of colour display, UV laser and biomedicine. The results not only expand the knowledge of the properties of lanthanide orthovanadates luminescence, but also contribute to the principles of the crystal growth and dimension transition of this kind of inorganic material.