Anthropogenic disturbances through land use conversion contribute to population extinctions and biodiversity loss. These modifications are associated with shifts in water quality, water flow, and light pollution. Artificial light at night (ALAN) alters the natural light and dark cycle in ecosystems. Light plays a key role in the ecology of organisms as a source of energy and information, a regulator of circadian rhythms, and a cue for communication, navigation, and orientation. Owing to urbanization, 40% of human populations are living in areas that are continually illuminated due to ALAN. Additionally, 50% of the human population lives within 3 km of aquatic ecosystems, making aquatic areas the most impacted by anthropogenic disturbances, such as ALAN. While ALAN is widespread, the consequences of ALAN have not been well documented, especially in freshwater species. Here we review the literature that examines consequences of ALAN on physiology, growth, and behavior in fish and amphibians. We focus on recent mechanistic studies using common species of tadpoles and fish along with an endangered species of salamander. We also explore the potential for populations to respond to selection from ALAN from the perspective of repeatability of the glucocorticoid response to ALAN exposure. We find that ALAN affects glucocorticoid hormones, growth, melatonin, and glucose levels, all of which can influence the fitness of aquatic organisms and may further drive biodiversity loss.