Monospecific Rhizophora spp. trees have been planted for several decades in the Philippines to offset heavy mangrove deforestation resulting from aquaculture pond construction. However, mangrove plantations show failures and success cases. The reforested mangrove studies are required for evaluating their ecological roles. We surveyed the forest structure, biomass, and net primary production (NPP) at an 18-year-old R. mucronata plantation site (PL) and a secondary natural mangrove site (NM) at Batan Bay Estuary, Philippines. The litterfall method and ingrowth core method were employed for NPP estimation. The survey showed that PL had a > 8,000 ha–1 tree density, 351.6 Mg ha–1 biomass, and 73.2 Mg ha–1 year–1 NPP, exceeding the values at NM. The low biomass quantity in NM was due to the residual effects of a typhoon in November 2013; however, the NPP showed a quick recovery which implies the disturbance-adapted characteristics of pioneer species. At PL, overcrowded conditions coursed to the large biomass and NPP, however monospecific Rhizophora spp. plantation has been known that vulnerable to the risk of stand destruction due to strong typhoons. We concluded they were different ecological roles between Rhizophora spp. plantations and natural mangrove stand.