The documentary, directed by Feras Fayyad and co-directed by Steen Johannessen, is a joint production between the two countries.
Claus Ladegaard, CEO of the Danish Film Institute, which help finance the film, called it a "powerful documentary".
"This nomination underlines Denmark's international strength in the documentary category. We succeed in making important and significant films that are shown and given recognition worldwide, including in Hollywood," Ladegaard said in a press statement.
The production team behind Last Men in Aleppo has previously received plaudits for the film, which follows three men as they risk their lives to take part in rescue work with NGO the White Helmets.
At last year's Sundance Film Festival, the film was chosen from a field of 12 for the award in the documentary category.
The difficult circumstances in which the film was made gave extra meaning to that award, producer Søren Steen Jespersen said.
"It is a huge release and recognition to be given this pat on the back. It means this is an important film," Jespersen said.
Documentary Strong Island, directed by American Yance Ford as he investigates the circumstances of his brother's death, is a fellow nominee for the documentary Oscar.
That film was edited by Dane Janus Billeskov Jansen and co-produced by Signe Byrge Sørensen, and also received funding from the Danish Film Institute.
Four Danish-made documentaries have been nominated for the Oscar for the Best Documentary Feature since 2010, though none have so far taken the prize.