Anti-predator vocalizations were studied in three species of tree squirrel, Callosciurus, in Ulu Gombak, Selangor Darul Ehsan, Malaysia. In the study area (ca. 10 ha), C. notatus was dominant in areas of low tree density, C. nigrovittatus in dense forests with tall trees, and C. caniceps in shrubs. All three species produced different calls to different predators; terrestrial carnivores, raptors, and snakes. Each signal caused conspecific individuals to adopt a different escape strategy. On hearing the repetitious, staccato barks toward carnivores, neighboring individuals ran up trees. A single bark was produced when raptors flew in the distance, which made conspecifics freeze. However, squirrels produced a rattle sound toward raptors in cases of close encounter. Squirrels moved toward the sound source of squeaks to snakes, and mobbed in a group. Calling frequency, intensity, duration, and sound structure of each call were compared among three species, and related to habitat selection.