This study assessed the influence of temperature on gonadal tissue maturation in the mangrove oyster Crassostrea gasar in the laboratory. The oysters were held at three water temperatures (18°C, 22°C, and 26°C), and the control oysters were maintained under cultivation in the environment. Every 10 days, 10 oysters from each treatment were examined for condition index and 10 for histological analysis. In the 22°C, 26°C, and field treatments, gonadal tissue maturation was observed, with no significant difference among treatments. The 18°C treatment was significantly different compared with the groups maintained at other temperatures, but did not demonstrate an improvement in gonadal tissue maturation. The results suggest that at 18°C, an accumulation of energy reserves occurs, and at temperatures greater than 22°C, gamete maturation occurs. In this study, the animals maintained in the field environment exhibited the same maturation conditions as those maintained in the laboratory, suggesting that this species can be stimulated in the laboratory, apart from the period of natural maturation.