Glau's first television credit was a guest role as a ballerina on the 2002 episode "Waiting in the Wings" of the television series Angel. There she caught the eye of director Joss Whedon, who later cast her in his critically acclaimed but short-lived TV series Firefly as River Tam, a role she reprised for the show's feature film sequel, Serenity. Glau previously auditioned for the role as a Pink Ranger on one of the Power Rangers series before meeting Joss Whedon.
Glau appeared on the episode "Love Conquers Al" of the TV series Cold Case. She had a small role in the film Sleepover, in which she played a high school senior named Shelly. She also appeared in the CSI episode "What's Eating Gilbert Grissom?", and the second season of The Unit; portraying Crystal Burns, the girlfriend of Jeremy Erhart. In 2006, Glau played Tess Doerner, a paranoid schizophrenic returnee in the second season premiere of The 4400 (episode "Wake-Up Call"), and became a recurring character from season 3 onwards. She also starred in the science fiction film Mammoth. Glau was cast in the ABC Family TV movie The Initiation of Sarah.
In Terminator: The Sarah Connor Chronicles, a series that debuted January 13, 2008, Glau played the role of Cameron Phillips, a Terminator infiltration unit sent back to protect John Connor and Sarah Connor from Skynet. The seventh episode of the series, "The Demon Hand", included several scenes in which Glau (in character as Cameron) dances ballet. Glau also guest starred as herself in the 2009 episode "The Terminator Decoupling" from the second season of the CBS situation comedy The Big Bang Theory.
On August 26, 2009, it was confirmed after much speculation that Glau would be joining the cast of Joss Whedon's Dollhouse for at least two episodes in the early part of the show's second season. She portrayed Bennett, the programmer for a rival Dollhouse.
On March 12, 2010, it was announced that she would be joining the cast of NBC's The Cape in a leading role. In June 2010 was confirmed as the female lead in the black comedy flick The Knights of Badassdom.
Glau voiced Kara Zor-El in the DC Comics original animated movie Superman/Batman: Apocalypse. She will reprise the role of Supergirl for the video game DC Universe Online.she got the part for power rangers .
|2002||Angel||Prima Ballerina||Episode: "Waiting in the Wings"|
|2002–2003||Firefly||River Tam||Series regular, 14 episodes|
|2003||Cold Case||Paige Pratt||Episode: "Love Conquers Al"|
|2004||CSI: Crime Scene Investigation||Mandy Cooper||Episode: "What's Eating Gilbert Grissom?"|
|2005–2007||The 4400||Tess Doerner||8 episodes|
|2006||Mammoth||Jack Abernathy||TV movie|
|2006||The Initiation of Sarah||Lindsey Goodwin||TV movie|
|2006–2007||The Unit||Crystal Burns||7 episodes|
|2008–2009||Terminator: The Sarah Connor Chronicles||Cameron Phillips / Allison Young||Series regular, 31 episodes|
|2009||The Big Bang Theory||Herself||1 episode The Terminator Decoupling|
|2009–2010||Dollhouse||Bennett Halverson||4 episodes|
|2010||Chuck||Greta||Episode: "Chuck Versus the Fear of Death"|
|2010||Deadly Honeymoon||Lindsey Ross Forrest||TV movie|
|2010||Superman/Batman: Apocalypse||Kara / Supergirl (voice)||Video|
|2010||Good Morning Rabbit||Lucy||Episode: "National Hamburger Day"|
|2010||The Knights of Badassdom||Gwen||Filming|
|2010||DC Universe Online||Supergirl (voice)||Video game; in production|
|2011||The Legend of Hell's Gate: An American Conspiracy||Maggie Moon||Completed|
|2011||The Cape||Orwell||Series regular|