Homalomena rostrata (Griff.) plant is one of the Araceae families that found in the Muanglee forest, Namuen district, Nan, Thailand. This plant is rich source of essential oils. Fresh stem and leaves of the plant are used in certain food preparation. Roots and rhizomes have been used as herbal medicine. In this research, antibacterial activities of essential oils and ethonolic extracts of roots, rhizomes, stem and leaves of H. rostrata (Griff.) were evaluated. Under hydrodistillation method, the essential oils from the rhizome, leaves, root, and stem were obtained in 0.09%, 0.03% 0.02% and 0.01%, respectively. On the other hand, the yield of the crude ethanolic extracts from soxhlet extraction method in rhizomes, leaves, roots, and stem were 1.90%, 1.70%, 1.74% and 1.53%, respectively. The obtained essential oils and the crude ethanolic extracts were examined the antibacterial activity against three species of bacteria i.e. Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 11778) and Escherichia coli (ATCC 25922), by agar disc diffusion method. The results showed that all essential oil and ethanolic extracts of rhizomes had inhibitory effect on the growth of Bacillus cereus. Essential oil of rhizomes was also potent inhibitor of stephylococcos aureus growth. On the other hand, all essential oils and ethanolic extracts were found inactive against gram negative bacteria; Escherichia coli. In general, inhibitory activity of essential oil was greater than that of their own ethanolic extracts. Among all essential oils and ethanolic extracts of H. rostrata (Griff.), the essential oil of leaves had the most inhibition on the growth of bacterial strains tested.