A general and facile oleic acid assisted hydrothermal method was developed to prepare colloidal rare earth orthovanadate (LnVO₄, Ln = Y and lanthanides) nanocrystals (NCs). The structure and morphology of samples were characterized with XRD, TEM, HRTEM and EDS. The as-synthesized NCs could be readily dispersed in nonpolar solvents and most of the LnVO₄ NCs shared a square sheetlike morphology. Particularly, the NCs of LaVO₄ and CeVO₄ would spontaneously self-assemble into an ordered nanostructure due to long chain molecules attached to their surface and their regular square shape. The formation mechanism was also investigated based on their crystal structures. Photoluminescence characterization showed that there is strong red emission from LnVO₄ : Eu (Ln = Y, La, Gd, Lu) NCs under UV excitation , which broadens the range of possible applications for these materials.