The best-selling author of the Inspector Rebus novels as agreed to help promote and raise funds for the £25 million Quaich Project.
If the funding for the project can be raised and planning permission is secured, it would see the existing Ross Bandstand in the gardens and a concrete bowl overlooking Edinburgh Castle replaced with a 5000-capacity amphitheatre and a two-storey complex with catering and hospitality facilities.
Rankin has been named as a "Quaich Bearer" who will be help to raise the profile of the plans for West Princes Street Gardens on the world stage over the next few years - along with actor Alan Cumming, singer-songwriter KT Tunstall and Kelpies creator Andy Scott, and American rock star Amanda Palmer.
The Edinburgh-based author said the existing bandstand, which dates back to 1935, was "not used nearly enough" because it had been allowed to fall "disrepair" over the years.
He said the proposed overhaul of the park would ensure it would be "more accessible and more beautiful" for future generations, pointing out that the proposed changes would make it easier for him to visit the park with his disabled son, who is in a wheelchair.
Rankin was filmed in the gardens in conversation with Broadway star Cumming after the Broadway star joined forces with Tunstall to launch the international fundraising campaign for the Quaich Project in New York.
Rankin's involvement has emerged months after he agreed to help promote a new campaign to safeguard the future of Edinburgh's World Heritage Site. He recorded video messages with Sir Tom Devine, the leading historian, and fellow author Alexander McCall Smith, in which they expressed concern about the threat of "unregulated tourism" and the "potential destruction of eminent sites."
Rankin described the Edinburgh World Heritage trust, which is charged with protecting the city's Old and New Towns, as the city's "champion” for its efforts to look after the city and for “making sure that the fabric of the city is well maintained but also that is a fantastic place for visitors and its inhabitants”.
EHW director Adam Wilkinson was on the panel which chose the winning design for the Quaich Project.
It is being pursued by a public private partnership set up by the city council and hotel developer Norman Springford, after the businessman agreed to help pay to revamp the gardens, which dated back to the 19th century.
He quit as chair of the project last week in the wake of criticism over the international fundraising campaign after leaked marketing brochures suggested that corporate backers and private donors would be able to secure the "naming rights" for parts of the gardens and would also have a "unique opportunity to network with our Quaich Bearers at numerous events throughout the world."
One of the brochures states: "Our Quaich Bearers are globally recognised Scots who act as ambassadors for the project on an international stage.
"We will be collaborating with these supporters to deliver a variety of specially planned performances and VIP events throughout the duration of the project. These events are designed to raise the profile of the project on the world stage and to engage key philanthropists and individuals overseas."
Rankin was unveiled as Quaich Bearer days after taking to Twitter to raise concerns over the condition of East Princes Street Gardens following the staging of an expanded Christmas market over the winter.
In the new promotional video for the Quaich Project, Cumming, a long-time backer of the American-led team behind the proposed overhaul of the gardens, tells Rankin that he was "obsessed with the idea of reinvigorating traditional spaces and bringing new energy and new ideas into parts of a city that haven’t been vital for a long time.
He said: "Here’s a thing that used to be about bringing people together, the bandstand as a community centre.
"We’ve lost that in the very centre of Edinburgh, and we are now trying to recreate that in a lovely, beautiful way that will bring people together in a 21st century way."
Speaking on the video, Rankin said: "Like everything in Edinburgh it’s got to be a balancing act.
"You’ve got that balance between the Old Town and the New Town and we’re right at the halfway point here at the gardens.
"But there has to be something for the visitor to do. You want to show them the city behind the city, not just the things they usually see; there is more to the city than that.
"And we’ve always got that balancing act between wanting to be modern but also wanting to be traditional.
"Making sure you respect tradition while being modern and I don’t think anybody is talking about huge radical changes to the structure of the gardens and I’m not talking about shutting the gardens off to the general public, but what they’re talking about is making what’s here more accessible and more beautiful.
Also, my son is in a wheelchair - my youngest son is in a wheelchair – and to make it more accessible some of the viewing areas which are being proposed up at actual Princes Street itself, ways of getting into the park, ways of getting into the grounds, or just getting a viewing spot would be great."
Cumming adds: "I just think it’s just a really great opportunity for people to come together in a way that they haven’t been able to for decades and also, not just at the (Edinburgh) Festival time, you know?
"I like the fact that, you know, it’s such a beautiful ancient city, and something is happening, a new sort of architectural thing is happening in the middle of it. But yet it doesn’t feel like a big kind of crazy glass box that’s happening."
Jules Haston, director of development with the Quaich Project, said: “Both Ian and Alan share our vision of West Princes Street Gardens becoming more accessible and useful space for small scale events run by community groups – a view echoed by the public in our most recent public consultation.”