Loach joined the full cast of The Angels' Share – including actors William Ruane and John Henshaw as well as rising new star Paul Brannigan.
And Glasgow actor and director Peter Mullen also turned out for the screening.
Speaking before the premiere at Cineworld in Glasgow's city centre, Paul said he was adjusting to becoming a well-known face.
The young dad, from Barrowfield, who had previously been involved in drugs and gang violence, was working at a community initiative when he offered the role.
Paul said he is slowly getting used to seeing his face go past him on the side of buses – and added that he's been getting lots of attention from fans.
The 24-year-old said: "I do get approached for autographs. Some people get jealous but I know how to deal with them without losing the rag."
The Angels' Share is the fifth film Loach has shot in the west of Scotland, and his 12th collaboration with Scottish screenwriter Paul Laverty, who has worked with Loach since 1996's Carla's Song.
Loach said: "Glasgow is a city built on struggle and that leads to a lot of strength and humour and resilience, which makes the city ideal for a film maker.
"You can tell any story here."
The 75-year-old director said he would now take a break before his next project.
He added: "I feel a bit of a break is in order, definitely."