He sought a warmer climate to recover from a lung problem, (perhaps tuberculosis), first traveling to Australia in 1849, and then the Philippines.

Six years after his arrival, he and nine other Honolulu physicians petitioned to charter an organization called the Hawaiian Medical Society.

After the death of Thomas Charles Byde Rooke in 1858, he was appointed physician to the royal family of King Kamehameha IV.

He had three main goals: to find sources of labor for the sugarcane plantations, to learn about the latest treatments for leprosy, and to collect and import plants and animals that would be useful to the Islands.

[6] Another European immigrant to Hawaii, Joseph Francis Charles Rock (1884–1962) would continue Hillebrand's work of identifying Hawaiian species.

In 1880, he determined that would never happen, so sold his home to shipping entrepreneur Captain Thomas Foster and his wife Mary, who lived on an adjacent lot.

Specimens collected by Hillebrand are cared for at herbaria worldwide, including the National Herbarium of Victoria (MEL), Royal Botanic Gardens Victoria,[11] the Natural History Museum of the United Kingdom, the Peabody Museum of Natural History and the Royal Botanic Gardens Edinburgh.