Visible crew/equipment: As Ellie runs up the stairs of the observatory after hearing the first audio transmission from space, she runs towards doors with two large glass windows in them. As she opens the doors, a crewman/cameraman is visible in the right window for a brief fraction of a second.

Continuity: There's a scene where Ellie sleeps with Palmer, then gets up quickly to go to the lab. In her haste, she departs whipping on a shirt with no bra. The camera follows her outside where suddenly it appears she is now wearing one.

Factual error: When Mr. Hadden reviews Ellie's life history on his airplane, he says she graduated from MIT 'magna cum laude'. This is impossible, as MIT does not award academic honors to graduates.

Deliberate "mistake": The slew rate of the radio telescopes at the VLA has been greatly increased for the movie. They are actually quite slow and make little to no noise.

Continuity: If the cameras inside the Sphere won't work because of the magnetic field that is being given off by the machine, then why do the cameras on the main structure work?

Continuity: In the part of the movie where Ellie is traveling through the worm holes, in one scene it shows the restraint seat getting crushed against the top of the pod she's traveling in. However, when the camera shows Ellie inside the pod after she lands in the water, over her shoulder you can see the restraint seat in good condition. I realize some could argue that her trip never happened, but the special finding report, discussed at the end of the movie, proves her trip did in fact happen since her camera recorded 18 hours of static. Therefore, her restraint should have been crushed when the camera was showing it at the end of her trip.

Factual error: In the zoom-out at the very beginning, we hear broadcasts going back in time as we zoom out through the solar system. However, we hear broadcasts going back through time roughly 40 years. Shouldn't we be 40 lightyears out from Earth to hear them, rather than just in the Oort Cloud beyond Pluto? Radio waves travel at the speed of light like any electromagnetic wave. EM waves should not be confused with sound waves, which move much slower than the speed of light.