The hilsa fish (Tenualosa ilisha) is highly sought after by the community in Labuhanbatu Regency, Indonesia. The population of the hilsa fish has been declining in the waters of North Sumatra Province. It is, believed to be linked to the excessive exploitation of the hilsa fish resources by local fishermen, the practice of catching the hilsa fish during their spawning period, deteriorating water quality, and degradation of the mangrove areas that serve as their breeding habitat. This study aimeds to analyze the mangrove community structure along the coastal waters of the hilsa fish spawning habitat, to assess the influence of mangrove density on water quality, and to examine its impact on the feeding habits of the hilsa fish. The method used was the transect line method. The findings of this study revealed the presence of 13 true mangrove species in the research location. The mangrove species most commonly found at nearly every station is Rhizophora apiculata. Values of relative density (Rd), relative frequency (RF), and relative dominance (RD) were determined for each level of mangrove growth: seedling, sapling, and tree. Meanwhile, the importance value index (IVI) values indicate that the species with a better chance of maintaining their growth and survival is Rhizophora mucronata. The results of the linear regression analysis testing showed that the mangrove density does not significantly impact water quality parameters, such as temperature, turbidity, salinity, dissolved oxygen, nitrate, biological oxygen demand, phosphate, and lead. In addition, gastric analysis of the hilsa fish stomach content revealed that the most consumed food type by the hilsa fish is the mangrove detritus, accounting for 51% of the total gut content. This underscores the crucial role of mangrove availability as a feeding ground for the hilsa fish.