Bryde’s whales, Balaenoptera edeni, are the only year-round resident baleen whale in the Gulf of Mexico, have an estimated abundance of 33 individuals (CV 1.07) in the Gulf of Mexico population, and are found within a restricted range near the De Soto Canyon in the northeastern Gulf. Based on their localized distribution, low abundance, and recent evidence that this population represents a unique evolutionary lineage and exhibits very low levels of genetic diversity, the Natural Resources Defense Council (NRDC) has petitioned NMFS to list the Gulf of Mexico Bryde’s whale as an endangered species and define critical habitat to enhance their protection. The NRDC highlights the high levels of anthropogenic noise from shipping and seismic surveys in the Gulf of Mexico as a major stressor. Historical whaling records found balaenopterids, most likely Bryde’s whales, throughout a broader area than their currently known range, including the western and central portions of the northern Gulf of Mexico, though sightings are now rare in this region, despite substantial effort. Autonomous passive acoustic methods are the most successful tool for finding rare whale species in areas where they occur infrequently and areas where they were historically sighted by whalers. The objectives of this study are to collect passive acoustic data for use in investigations of 1) Bryde’s whale occurrence and distribution, and 2) ambient noise conditions in the western Gulf of Mexico. We deployed 5 calibrated autonomous acoustic instruments over a one year period from June 2016 – June 2017 along the 200 m isobaths throughout the western Gulf of Mexico predicted Bryde’s whale habitat. This will provide data to investigate whether, where, and when Bryde’s whales occupy this habitat and will be useful in designating critical habitat if this species is listed under the ESA. By using calibrated instruments, an additional goal will be to obtain data to characterize the ambient sound environment at these sites to determine whether acute or chronic anthropogenic noise sources pose a risk to this species.