Mangrove is known as a unique and complex ecosystem, located in the intertidal zone vulnerable to anthropogenic pressures. In this study, we analyzed the floristic composition and relationship between species density and soil properties of mangrove forests in Teluk Adang Nature Reserve (TANR), East Kalimantan, Indonesia. Data were collected by establishing 6 transects placed perpendicular to the sea. The results showed that there were 14 species of mangroves in TANR. The current remaining stand has not been disturbed by human intervention. Rhizophora apiculata dominated all growth strata (seedlings, saplings, and trees) with the Important Value Index (IVI) of 98.22%; 127.73%, 144.03%, respectively. Ecologically, the density and distribution of Rhizophora apiculata correlated with soil texture conditions such as silt and clay. The tree density of mangroves in TANR was classified as low with an average of 606.67±147.230 ind ha^-1. The average values of diameter, height, and basal area were 18.16±2.119 cm; 12.24±2.667 m; 42.56±2.255 m ha^-1, respectively. The Margalef species richness index and Shannon Wienner diversity index in TANR were in the low-to-moderate category. To improve the condition of the disturbed mangrove forests, it should be immediately restored by considering the result of the analysis of the current composition and structure of mangrove vegetation.