She made her television debut on the sitcom Veronica's Closet, before guest appearances on Love Boat: The Next Wave, CSI: Crime Scene Investigation, JAG and starring as Medea in a television movie adaptation of Jason and the Argonauts (2000). She also appeared in the movie On the Edge (2001) and the miniseries The Diamond Hunters (2001) before being cast on Star Trek: Enterprise.
She is married to Michael Rapino, CEO of Live Nation. The two met when he booked her for a beer commercial in Los Angeles. He lived in England and while working on Star Trek: Enterprise, she found conducting a long-distance relationship difficult, running up an "astronomical" phone bill. She proposed to him and the two married in Negril, Jamaica, on April 22, 2003. They have three children.
She was scheduled to appear on an episode of Lost during the 2005–2006 season as a former love interest of Sawyer (Josh Holloway). Though she filmed some scenes, the flashback scenes in that episode were changed from Sawyer to Michael (Harold Perrineau) and her scenes were never used in an episode nor featured as "deleted scenes" in the DVD set's bonus material. Set photos from the shooting of a scene surfaced in 2008.
She played Captain Lola Beck in Starship Troopers 3: Marauder, which was released directly to DVD in the United States on August 5, 2008.
She made an appearance on the House episode titled "Teamwork" as Lexa, the wife of the porn star featured as the patient in this episode (airdate: November 16, 2009).
Blalock had a supporting role as Stacy in the william Kaufman action thriller Sinners and Saints, set in post-Katrina New Orleans, which premiered in Los Angeles on June 30, 2010.