Heather McGowan, 32, will join the A-list star at an event being held at a secret location in the Scottish capital.
Clooney is visiting the city after accepting an invitation from the owner of sandwich shop Social Bite, which helps the homeless by allowing customers to pay for food and drink on their behalf.
It operates a suspended coffee and food programme where customers can pay for a hot drink or food for a homeless person.
Josh Littlejohn is the co-founder of the social venture and approached Clooney earlier this year about visiting the not-for-profit chain.
The actor-director agreed and he is expected to meet employees at the Edinburgh shop tomorrow and deliver the keynote address at the Scottish Business Awards, also founded by the entrepreneur.
McGowan, who runs a wedding events company in Glasgow, said she was shocked to discover she had won the competition organised by deals and events site itison to raise funds for Social Bite and the humanitarian charity co-founded by Clooney Not On Our Watch.
“I’m a big George Clooney fan and love the Oceans films, so I’m absolutely delighted, and still a bit in shock, to have won itison’s competition,” she said.
Last month, Social Bite launched what is thought to be the first ”selfless” loyalty card which lets customers feed the homeless.
It works by saving up loyalty points to buy a homeless person a free meal and hot drink after 10 visits to the cafe.