The successful applicant will be "hands-on" with plenty of previous experience and the agility of a "mountain goat".
The job on St Michael's Mount comes with its own house in the village and the chance to become part of the "friendly island community". Duties include abseiling down the castle to care for its exotic garden.
Situated 500 yards off the coast of Cornwall, the St Michael's Mount is reached by ferry boats which run between Marazion and the island's harbour. A causeway, which is submerged under water at high tide, is the only land route between the island and the mainland.
"Gardening on a rock in the middle of the sea isn't for the faint-hearted, nor is abseiling from the battlements of a castle," the job listing reads.
"But the garden team on St Michael's Mount take all this in their stride as well as the general terrain which would challenge the most agile mountain goat."
It adds: "Beyond the physical challenges, the garden team are passionate about the island's unique garden and continue to develop the plant collection using species that thrive in one of the UK's most challenging environments."
Legend has it the castle was built by a giant called Cormoran who would go ashore to raid livestock from local farms. A reward was offered in return for killing the giant and a young boy called Jack slayed the beast and became a local hero. He was subsequently hailed as "Jack the Giant Killer".
The island takes its name from St Michael who supposedly appeared to a group of fishermen in 495 AD.
The oldest surviving buildings date from the 12th Century, when a Benedictine priory was founded there. Following the English Civil War, the island was acquired by the St Aubyn family, who still live in the castle.
In 1954 the family went into partnership with the National Trust and the castle and its grounds were opened to the public. It now attracts over 65,000 visitors from April to September. The Mount is home to about 30 residents, has its own church, ancient harbour and gardens full of exotic flora.