DNA barcodes (i.e. cytochrome c oxidase subunit I or COI in the mitochondrial genome) obtained from 7 dog breeds sampled in the Philippines and 8 dog breeds in the United States retrieved from GenBank were analyzed using Neighbour-Joining method based on Kimura 2-parameter model in MEGA5. Based on 671 COI positions, overall genetic diversity of dog breeds was 2.9%. Average genetic distance was higher among dog breeds sampled inthe Philippines (d=0.033) than among GenBank-derived samples (d=0.001). Average pair-wise distances between dog breeds sampled locally and those accessed from GenBank was 0.043 unit. Our results indicate that DNA barcodes can be effective in differentiating between breeds sampled in the Philippines, but not among dog breeds whose COI sequences where derived from GenBank. No genetic basis for grouping breeds based on their functional type is suggested. Dogs of the same breed from the two countries do not have the same COI sequences. Genetic distances between dog breeds from the United States were too small to identify introgressions and conclusively determine their origins and diversification. More COI sequences should thus be determined from distinct breeds and mixed-breed populations to improve reliability of using DNA barcodes to confirm breed origin of a dog.