<p>This study investigates the scintillation performance of Eu³⁺-doped GdBO₃ nanophosphors synthesized via an acetylacetone-assisted aqueous sol–gel route for potential radiation detection applications. While previous studies primarily focused on structural and photoluminescence properties, the present work evaluates their detection response under X-ray and γ-ray excitation using prototype powder-based scintillation samples. The effects of Eu³⁺ concentration (0.5–20.0 at%) at fixed pH = 2.0, as well as precursor pH (2.0–10.0) at a constant Eu³⁺ content of 10.0 at%, on radioluminescence intensity, light yield, and energy resolution were systematically examined. The emission spectra exhibit the characteristic ⁵D₀ → ⁷F_j transitions of Eu³⁺, indicating effective luminescence from the activator ions. Under 662&#xa0;keV γ-ray excitation from a ¹³⁷Cs source, the optimum scintillation performance was achieved for the sample containing 10.0 at% Eu³⁺ synthesized at pH = 10.0. This enhanced response is attributed to more efficient energy transfer processes together with reduced concentration quenching. The optimized composition exhibited a light yield of approximately 24,000 ± 4,800 ph/MeV and an energy resolution of 7.9% (FWHM). These findings highlight the strong potential of GdBO₃:Eu³⁺ nanophosphors as cost-effective scintillation materials for radiation detection and imaging applications.</p>