Triclinic Gd1-xEuxBO3 nanophosphors have been prepared by a hydrothermal method without using additional coreagents and prior precipitation of precursor (in situ). The formation of the borate nanorods and their crystal structure was refined on the basis of X-ray diffraction patterns (XRD) and well confirmed using various techniques such as infrared spectroscopy (IR), Raman spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The new triclinic crystal structure (space group P1) for the GdBO3 nanocrystals and detailed structure parameters were determined with the help of the Rietveld analysis. The spectroscopic characteristics of the synthesized nanomaterials with different concentrations of Eu(3+) ions were defined with the use of luminescence excitation spectra as well as emission spectra and decay kinetics. The Judd-Ofelt parameters (Ω2, Ω4) and quantum efficiency, η, were also calculated for the more detailed analysis of Eu(3+) spectra in the GdBO3 host.