The National Trust for Scotland, which owns the islands, is launching the Love Our Islands campaign to support historical conservation and environmental work on the archipelago.
The appeal marks the 30th anniversary of St Kilda's designation as a World Heritage Site.
The islands lie about 40 miles west of Benbecula in the Outer Hebrides.
St Kilda is home to hundreds of thousands of seabirds which nest on the seven islands that make up the archipelago.
It was also the home of generations of people until the last were evacuated in 1930.
The last surviving former resident of St Kilda, Rachel Johnson, died earlier this year at the age of 93.
Caring for St Kilda costs the National Trust of Scotland £270,000 a year. It includes preserving the street the residents once lived on, the church, nearly 1,400 "cleits" - conical stone structures used for storage and drying of seabirds - and buildings which are thought to be prehistoric.
The trust also monitors wildlife on St Kilda, which is the largest seabird colony in the north-east Atlantic with 600,000 nesting birds each year.
The most recent major survey, conducted last year, revealed dramatic declines for seabirds including fulmars, kittiwakes, common guillemots and razorbills, amid rising temperatures and rising seas, the trust said.
St Kilda was designated as a natural World Heritage Site in 1986 after being one of the first sites put forward in the UK for the designation.
In 2005, it became the UK's first site to have mixed listings for both natural environment and cultural value.
National Trust for Scotland chairman Sir Moir Lockhead said: "Its remote location, outstanding natural beauty and the dramatic story of the people who once lived there have captivated people across the centuries and it still holds an allure for many people today.
"More importantly, anyone who cares about our seabirds and the wider health of our oceans will appreciate the work we carry out here year on year at St Kilda.
"Our seabird survey from St Kilda is providing us with vital information which appears to show major impacts of climate change on sea conditions and the species which depend on the marine environment."
A new fundraising appeal is being launched to look after the remote islands of St Kilda.