A study was conducted in a mixed mangrove forest in Pulau Ubi, Pengkalan Kubur to determine the floristic composition and diversity. A total of 10 rectangle study plots measuring 25 x 20 were established which equivalent to 0.5 ha. Based on 122 individuals collected, 29 families were identified. The plant inventory includes the measurement of diameter at breast height of adult trees from 0.05 m. The mangrove species in Pengkalan Kubur showed moderate diversity with a Shannon-Weiner Index,H’ value of 2.73. Meanwhile, the Pielou Evenness Index was 0.75 and the Margalef Richness Index 8.12. These findings underscore the significance of mangrove forest and act as baseline for the protection from ongoing and future sustainability.