Parental care is a critical component of many breeding systems that enhances both parent and offspring fitness. It is widely recognized that parental care varies in quality and quantity in response to variation in offspring need, parental condition, and ecological context. One context that has been underexplored, however, is the difference in parental care between day and night, with many parental care studies focused on diurnal care. To fully understand the evolution of parental care, the costs and benefits and the negotiations between parents, both diurnal and nocturnal care must be accounted for. Here, we show that nocturnal parental care exists in the clownfish Amphiprion percula, with males and females actively caring for offspring at night throughout embryo development and during hatching in a laboratory setting. At night, as during the day, males are the dominant caregivers and both parents increase care as embryos mature. At night, in contrast to the day, females provide substantially more care. This increase in energy expended by parents on care may be a mechanism to increase dissolved oxygen in the water at night, improving embryo survival. We also document the existence of three new nocturnal parental care behaviors, not previously seen during the day: vigorous fanning, vigorous mouthing, and anemone biting. These behaviors are particularly frequent during hatching, and although they are not necessary for hatching to occur, they may serve to enhance the embryos’ successful transition from the benthos to the water column. This study contributes to our understanding of parental care, demonstrating the importance of considering nocturnal care if we are to gain a complete understanding of the evolution of parental care. / 2023-03-16T00:00:00Z