Characterization of rumen microflora is needed to understand rumen fermentation. Conventional culture-based methods are unreliable because cultured microorganisms represent only a small fraction of the natural microbial community. The present study used metagenomics in determining the rumen microbial diversity of the Philippine carabao through 16S rDNA analysis. Community DNA was extracted from rumen fluid obtained from two carabaos fed with grass. PCR amplification using bacterial universal primers was done and a 16S rDNA library was constructed. The library comprised of 147 clones and 46 of these were sequenced. One (1) clone was identified as Pseudobutyrivibrio ruminis, and three clones were identified as Butyrivibrio fibrisolvens. Furthermore, 9 out of the 46 clones shared similarity ranging from 90-96% with known bacteria while the similarity of the remaining 33 clones was less than 90% of those of known bacteria. Phylogenetic analysis showed that the bulk of the sequences clustered with the Firmicutes phylum (formerly known as low G+C subdivision) (67.4%). The other sequences clustered with the Cytophaga Flexibacter Bacteroides subdivision (17.4%), Proteobacteria (8.7%), one clone (ADSC105) to the Synergistetes group (2.2%) and one clone (ADSC 89) to the Planctomycetes phylum. These results showed that the Philippine carabao has a diverse bacterial population in the rumen that is different from those of cattle and other ruminants. This is the first report of a 16S rDNA library from carabao rumen.