Vo filme Znamenia hrajú Mel Gibson (Graham Hess), Joaquin Phoenix (Merrill Hess), Rory Culkin (Morgan Hess), Abigail Breslin (Bo Hess), Cherry Jones (Officer Paski), M. Night Shyamalan (Ray Reddy), Patricia Kalember (Colleen Hess), Ted Sutton (SFC Cunningham), Merritt Wever (Tracey Abernathy), Lanny Flaherty (Mr. Nathan), Marion McCorry (Mrs. Nathan), Michael Showalter (Lionel Prichard), Kevin Pires (Brazilian Birthday Boy), Clifford David (Columbia University Professor), Rhonda Overby (Sarah Hughes), Greg Wood (TV Anchor), Paul L. Nolan (Mexico City Reporter (voice)), Ukee Washington (Off-Screen TV Anchor (voice)), Babita Hariani (Car Radio Voice (voice)), Adam Way (Radio Eye Witness (voice)), Angela Eckert (Soda Commercial Girl), Jose L. Rodriguez (Radio Host (voice)), Paul Wilson (Soda Commercial Singer (voice)), Thomas Griffin (Soda Commercial Singer (voice)), Derek Mears (Alien on the Roof (uncredited)), Chuck Pressler (Fireman (uncredited)).