Determining variation in marine species’ sensitivity to ocean acidification is critical for future success of marine ecosystems under changing environmental conditions. Reproduction is critical for individual and population success, yet is energetically expensive and is predicted to be adversely affected by ocean acidification in many marine organisms. We investigated the effects of projected future CO₂ levels in the ocean on reproductive output of two species of damselfish, Amphiprion percula and Acanthochromis polyacanthus. Adult breeding pairs were held under three CO₂ treatments: current-day control (365 μatm), moderate CO₂ (658 μatm), and high CO₂ (1023 μatm) for a 7-month period that included the summer breeding season. Reproductive output increased in A. percula, with more pairs breeding and a 30% increase in the number of clutches produced per pair in the high CO₂ group. In contrast, A. polyacanthus exhibited a significant decrease in reproductive output, with fewer pairs breeding and a 37% reduction in the number of clutches produced per pair. Despite the variation in reproduction for these two species, neither species showed a difference in parental conditioning between control and high CO₂ treatments. Our results demonstrate contrasting impacts of ocean acidification among fish species, even within the same family. A greater understanding of the impacts of ocean acidification on reproductive performance is required to predict the consequences for future populations of marine organisms.