The Michael Powell Award for best British feature went to Joanna Coates's Hide and Seek, which had its world premiere at the festival and which also features "scheduled partner swapping."
Ms Coates said: "We set out to make a film that uses beauty and playfulness to speak about our deeper feelings."
She was one of several film-makers honoured at the awards ceremony for the 68th EIFF, held at the city's Filmhouse.
British actor Eddie Marsan picked up the best performance award at the festival.
The screen star, known for films such as Happy-Go-Lucky, War Horse and Hancock, picked up the award for best performance in a British feature film.
The honour was for his performance in the film Still Life, "a poignant tale of life, love and the afterlife".
Other films recognised included Midi Z's Ice Poison, which won the award for best film in the international competition.