Metal pollution is a major threat in tropical areas due to increasing pressure from anthropogenic activities along coastlines. Unfortunately there are very few toxicological studies that assess the effects of metals on marine organisms in tropical areas. To help fill this gap, this study investigated how Cu alters the fertilization success of the coral Montipora capitata over several nights of spawning. Results indicate that gametes of M. capitata are sensitive to Cu pollution, with EC50 after 3 h ranging from 16.6 to 31.7 mg l-1. Moreover, the sensitivity of the gametes to Cu toxicity was influenced by the night of spawning during which fertilization experiments were performed. This result likely reflected changes in the quality of gamete over the spawning period.