Data on cetacean ecology are important for monitoring animals and developing conservation and management strategies in a specific area, and are crucial in the decision making process during the creation of marine protected areas (MPAs). Cetacean occurrence, distribution and behavior were investigated in Santa Monica Bay, California (1997-2007). A total of 425 boat-based surveys documented three species inhabiting the bay year-round - the common bottlenose dolphin, Tursiops truncatus, the long-beaked common dolphin, Delphinus capensis, and the short-beaked common dolphin, D. delphis - and ten species occurring occasionally. Coastal bottlenose dolphins were mostly found traveling, diving and feeding in waters within 0.5km of shore in 81.4% of the sightings (n=221), but were also observed occasionally in offshore waters. All other species were seen >0.5km of shore, often feeding near escarpments and submarine canyons. Endangered species such as blue whales (Balaenoptera musculus), humpback whales (Megaptera novaeangliae) and northern right whale dolphins (Lissodelphis borealis) were also recorded in the bay. The presence of a rich and diverse cetacean fauna suggests the need for long-term monitoring and a precautionary approach toward these species. These data are also essential in conservation and management decisions associated with the current creation of a MPA in Santa Monica Bay.