YouTube channel Time to Unite posted a clip of astronauts floating in zero gravity.
But, according to the male narrator, they are in fact hanging from wires in a mock-up ISS.
He said: “Inside [the ISS] there are a couple of zero gravity tricks that they use to fake it.
“The first is they have a complete mock-up built inside an airplane.
“The airplane does a bunch of rise and falls it does an upside parabolic trajectory and that simulates zero gravity.
“The other main way they simulate the zero gravity is with suspension in front of a blue screen and they use that trick for extended periods of time, for longer than 45 seconds segments, but they can’t move around as much, they can’t do the acrobatic flips and rolls in the extended mode.”
In one clip, retired NASA astronaut Chris Hadfield – wearing a red top – is seen bending down inside the ISS.
The back of his shirt appears to stick up as if attached to something.
“You expect wires to come in on either side of that harness in order to support it,” the narrator added.
“Of course, they have computer-graphiced (sic) out the supporting wires so you can’t actually see them.”
A crop circle near Raisting, Southern Germany
It isn’t the first time wacky theories have circulated claiming of a NASA cover-up.
Earlier this month, a clip showing an astronaut’s visor on the moon appeared to show another man without a spacesuit – sparking claims it was actually filmed inside a studio.
Of course, there is a mountain of evidence that proves the ISS is in space.
A live stream is regularly posted showing phenomenal images of Earth and the station itself can be seen in the sky at certain times.