Radiation-induced damage in quartz from the overlying Athabasca Supergroup sandstones and the basement host rocks at the Arrow uranium deposit in the southwestern margin of the Athabasca basin, Saskatchewan, has been investigated by electron paramagnetic resonance (EPR) spectroscopy as well as cathodoluminescence (CL) imaging and spectroscopy. Powder EPR spectra confirm that quartz from the Arrow deposit contains a suite of radiation-induced defects, including characteristic silicon vacancy hole centers formed from bombardment of α particles emitted from the radioactive decay of U, Th, and their daughter isotopes. The EPR intensity distribution of α particle-induced defects in detrital quartz close to the sandstone–basement unconformity suggests that uranium-bearing fluids at Arrow are restricted to areas directly above the basement-hosted mineralization. Pink quartz in the basement, which occurs as veins and breccias in spatial association with uranium mineralization, is characterized by elevated, homogeneously distributed radiation-induced defects, suggesting its crystallization from uranium-bearing fluids most likely linked to the main mineralization event. Smoky quartz in veins and cavities often exhibits characteristic α particle-induced CL rims, which crosscut the growth zoning and apparently record late uranium remobilization. Abundant radiation-induced defects in the basement at the Arrow deposit are restricted to quartz within ∼7 m from uranium mineralization, confirming structurally controlled fluid flows. These results highlight the application of radiation-induced defects in quartz for determining the loci of uranium-bearing fluids.