Visible crew/equipment: As Quatermass drives back to the spaceship in a cab, just before it is to be drilled, the film crew can be easily seen in the cab's windows. A woman with a white cap can be seen holding a script. Later when the police use a megaphone on their car to announce the spaceship is a hoax, you can again see the same woman with a white cap in one of the windows of the police car.
Continuity mistake: At the beginning of the film when the first skull is found, the black workman is holding a cigarette in his right hand when he tosses the skull to the foreman: The next shot cuts in and the foreman says "It may be worth money" the cigarette is now in the left hand of the black workman.
Plot hole: When Quatermass is being admonished by the senior minister for talking to the press, Breen gives his own theory to explain the presence of the spaceship: He says that it was used a propaganda weapon in 1944 and that the figures inside were made up of scraps old skin and bone, why was he unable to explain how the hull of the spaceship was heat resistant up to 3,000 degrees and harder than diamond?
Visible crew/equipment: From the first shot, the flashing yellow crossing beacons on Hobbs Lane are powered by cables that lie in full view over the set pavements.
Character mistake: Colonel Breen theorises to Quatermass that the spaceship is an experimental German V-weapon from the second world war: However according to the story, the underground station (Hobbs End) was dug in 1927: The V-weapons first landed in London in 1944, so how was it possible for a V-weapon to land where it did underground, impacted soild in clay right next to a deep level underground railway station seventeen years later without anyone noticing at the time? Breen should realise that his theory makes no sense.
Continuity mistake: When Roney and Barbara get out of the taxi, the street is in shadow, but in the next shot the sun is up, as it lights up the buildings in the background:. (00:36:05)
Revealing mistake: When Roney enters the spaceship, just before he first helps Quatermass to remove the insects from the their chamber, he is wearing gloves. Then in a shot from inside the hull of the ship, he is not wearing a glove on his left hand. When he reappears outside, he is wearing gloves. (00:39:56)
Continuity mistake: Just after the discovery of the insects in the spaceship, Roney runs out to tell Barbara to call the institute. Notice in between shots Barbara is standing on her own, then in the next shot a bemused Captain Potter suddenly appears standing right next to her. (00:38:53)