* Jenny Lerner (Téa Leoni) - Astronomy graduate student who discovers the incoming asteroid.
* Max Wolf (Elijah Wood) - Jenny's neighbor and assistant, who helps her with her research.
* Ellie Stanton (Vanessa Redgrave) - A billionaire astronaut and former NASA Director.
* Mike O'Neill (Morgan Freeman) - Former Space Shuttle commander and the current chief of NASA.
* Gus Partenza (James Cromwell) - An astronomer who helps Jenny and Max track the asteroid.
* Orlene Pilenski (Mary McDonnell) - A single mother and astronaut selected for the Space Shuttle mission to destroy the asteroid.
* Jason Lerner (Leelee Sobieski) - Jenny's younger sister, who is stranded in Washington, D.C. during the crisis.
* Robin Lerner (Laura Innes) - Jenny and Jason's mother.
* Monsignor Matthew Declan (Maximilian Schell) - An elderly Catholic priest who offers spiritual guidance to the President during the crisis.