The present study evaluated the ecological response of fish fauna to hydrological restoration in a mangrove area in Terminos Lagoon in the Gulf of Mexico. In two years, environmental parameters and ichthyofauna were obtained in a channel under restoration and a conserved channel. The fish fauna was composed of 12 species. As a result of the restoration process, changes in composition and abundance of some species were detected. The presence of visiting marine species Bathygobius soporator and Eucinostomus melanopterus, and an increase in the abundance of resident fish, livebearers species, were recorded. Richness, diversity, and evenness vary significantly between channels. Generalized linear mixed models indicated that the abundances of resident and overall fishes were significantly related to water depth, temperature, and salinity. The results suggest that fish are an ecological indicator of the mangrove reconnection with the Terminos Lagoon and the restoration of natural tidal flow in the short term. Long-term systematic monitoring of fish fauna will promote a better understanding of the restoration of mangroves and corresponding changes in the function of this ecosystem.