The creator of the number one Ladies' Detective Agency recently bought the uninhabited Cairns of Coll in the Hebrides for just under £300,000.
The remote chain can only be reached by boat, its inhabitants include seabirds and seals whilst minke whales and basking sharks frequent surrounding waters.
But the Scot admitted he is "embarrassed" to be referred to as their owner and is looking after them for the "nation."
McCall Smith, a keen sailor, fell in love with the isolated outpost after dropping anchor and enjoying a picnic on the white sandy beaches.
He promised the previous owners he would take care of the islands, buying the land in June last year. McCall Smith said: "I am embarrassed to use the term 'owner'.
"I do not own these island as I own my clothes.
"I am the person to whom the legal system of Scotland has given custody of this sacred spot, and that is something quite different.
"I intend to do absolutely nothing with them, and to ensure that, after I am gone, they are held in trust, unspoilt and uninhabited, for the nation."
Cairns of Coll, consists of a little group of islands north of Coll, one of the twin Argyll Atlantic islands of Coll and Tiree.
Famous for its beauty, McCall Smith wants wildlife to thrive and people to experience and enjoy one of Scotland's best kept secret.
He said: "I want to keep them in perpetuity as a sanctuary for wildlife, for birds and seals and all other creatures to which they are home.
"I want people to sail past them and marvel at them, as long as nobody leaves anything behind, I want people to set foot on those beaches and feel the sand between their toes and the wind in their hair.
"To have their hearts broken by the sheer beauty of these tiny slivers of Scotland."