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Toothed whales use echolocation to sense their environment and capture prey. However, their reliance on acoustic information makes them vulnerable to sound exposure. Odontocetes modify echolocation signals in response to ambient noise levels, yet the metabolic cost of producing and modifying echolocation signals are unknown. Studies on bats found that the metabolic cost of producing echolocation signals and modifying sonar parameters is high. Unlike terrestrial mammals, however, the conservation of oxygen is paramount for odontocetes that echolocate underwater on a breath-hold. Flow-through respirometry was used to determine the metabolic costs of producing and modifying echolocations signals in two trained bottlenose dolphins (Tursiops truncatus) that produced echolocation clicks with variable sound energy levels. Unlike bats, the metabolic cost of echolocation was negligible in dolphins. On average, the metabolic rate of submerged dolphins producing clicks was 1.1 times greater than the metabolic rate of submerged, silent dolphins. Similar to bats, the metabolic cost of producing echolocation signals increased significantly with acoustic energy in dolphins. Yet, for the sound energy levels produced, metabolic rates of dolphins producing clicks were within the range of metabolic rates measured when the dolphins were silent. These results can be used to better understand some of the energetic costs associated with dolphin foraging behavior as well as assess the relative energetic impacts of different delphinid behavioral responses to anthropogenic disturbance.