This paper provides a preliminary report on the different types of habitats including ecology and species diversity of Balbalasang-Balbalan National Park (BBNP) based on the Rapid Site Assessment (RSA) conducted along various microhabitat gradients in 2009. A total of 84 families, 206 genera and 319 taxa were recorded, including a new species of Rafflesia, a very rare parasitic plant. There are 106 Philippine endemics reported, 38 of which are Luzon endemics. 18 taxa were listed under either the Philippine Red List (Fernando et al., 2008) or on the IUCN Red List of Threatened Species (IUCN 2010). Result of the RSA conforms with previous studies revealing high, yet poorly understood biological diversity in this part of Cordillera. It further implies that BBNP support a large percentage of the country’s threatened, endemic, and unknown flora. A more comprehensive biodiversity assessment is therefore necessary to better account for the floral diversity of BBNP.