Not Another Happy Ending, which tells the story of a successful author, Jane Lockhart, who is suffering from writers block, also stars French actor Stanley Weber, Bafta nominee Iain De Caestecker, Henry Ian Cusick, Kate Dickie, Gary Lewis and Freya Mavor.
The film is directed by John McKay and was shot in Glasgow late last year.
It will receive its world premiere at the closing ceremony of this year's Edinburgh International Film Festival on June 30.
Watch the trailer below
Speaking about her first major movie role, Gillan said: "The film came about when I was working on We'll Take Manhattan, and my director John McKay said, "You're really good at falling over, you should read this script," and gave me Not Another Happy Ending.
"Playing the role really gave me the chance to immerse myself in the com-com genre, and before O played Jane, I watched in chronological order the greatest rom-coms of all time. I started with His Girl Friday, then The Apartment, which is amazing, and then I was naughty because I watched a later one because I couldn't wait to see Manhattan, then back to Annie Hall, before When Harry Met Sally. What I took from seeing them all was just how important the chemistry is between the two lead actors."