Widespread amphibian declines present one of the greatest challenges to conservation biology, with more than 40% of species at threat of becoming extinct. Despite decades of research, the significance of elevated ultraviolet-B radiation (UVR) in driving ongoing amphibian declines remains unresolved. This is partly due to the complexity of UVR exposures in the water column shaped by several environmental factors including riparian vegetation cover, water depth and turbidity, and a poor understanding of how parameters of exposure (dose, irradiance, and timing) affect amphibian health in both the immediate and longer terms. Through controlled laboratory experiments, we investigated the interactive effects of dose, irradiance, and timing of acute UVR exposure in aquatic life stages on long-term health of striped-marsh frogs (Limnodynastes peronii), including an assessment of physiological carryover effects that transcend metamorphosis. UVR-induced mortality in tadpoles was predicted by both irradiance and timing of exposure during development. Repeated diurnal exposures of tadpoles to high irradiance UVR caused disproportionate increases in DNA damage, resulting in detrimental carryover effects including delayed metamorphosis and epithelial depigmentation of metamorphosing frogs. This work provides a more holistic model for the impacts of complex UVR exposure regimes on amphibian health, with implications for the use of amphibians as aquatic bioindicators of environmental change impacts on relevant freshwater systems. We emphasise the need to consider delayed carryover effects when elucidating the effects of stressors such as UVR, not just on amphibians, but any other sensitive aquatic taxa that undergo ontogenetic or seasonal life-history transitions.