Mangroves are vital coastal ecosystems, notably present in the Savu Sea Marine National Park (SSMNP) in East Nusa Tenggara. This study evaluated sea environmental conditions (temperature, pH, salinity, dissolved oxygen, biochemical oxygen demand, and total suspended solids), alongside mangrove community structure and diversity. Using transect sampling, data were collected from 15 mangrove areas (45 plots) across the islands of Timor, Rote, Sabu, and Sumba, with plots sized for trees (10x10m), saplings (5x5m), and seedlings (2x2 m). Results identified eight mangrove species, including Rhizophora mucronata, which showed the highest importance value index for trees (165) and saplings/seedlings (200). A total of 513 individuals were recorded: 210 trees, 68 saplings, and 235 seedlings. Diversity indices ranged from 0.47 to 2.31 for trees and 0 to 1.55 for saplings/seedlings, indicating low-to-medium diversity and richness. Water conditions were found suitable for mangrove growth. This study provides a comprehensive baseline on mangrove diversity and environmental conditions, supporting conservation aligned with SDGs 13 (climate action), 14 (Life Below Water), 15 (Life on Land), and 8 (decent work and economic growth).