Eric Fellner, co-chairman of Working Title Films and producer of Darkest Hour, said filmmakers had received numerous "surprising" reports of audiences breaking into applause, admitting it "very rarely happens".
Darkest Hour ends with Oldman delivering Churchill's House of Commons speech of June 4, 1940, responding to the Dunkirk evacuation and vowing: "We shall defend our island, whatever the cost may be."
Asked about standing ovations and applause in ordinary cinemas, Fellner said: "It has been reported back to us, not only here but in America, and across the whole of the country not just in the big metropolitan areas.
"We've been hearing it a lot. It's very surprising. It very rarely happens other than at the premiere or special screenings of the films, so it's quite extraordinary.
"It's completely unusual, totally unusual.
"When we decided to make the film it was two years ago. We made the film because we believed it was a fascinating piece of history that most people don't know the detail of, that it was incredibly engaging and exciting in the way it was going to be told, and it was entertaining.
"Those were the reasons for making it.
"However, since then, the world has changed politically. We've had Brexit, we've had Trump, we've had all sorts of volcanic political and social eruptions and I think we've just hit a zeitgeist where people are fascinated by and feeling a need for leadership.
"This story goes beyond the reasons for which we made it, and now it's playing into those themes."
David Cowgill, from Knutsford, told the Telegraph: "Our small local cinema was packed and, at the end, a large section of the audience applauded.
"I asked myself if they were showing appreciation of a good film or was it the Dunkirk Spirit coming out.
"My gut reaction says it was the latter."
