By 1989, Benz's figure skating career had ended and she got involved with the local theater. Her first small movie role was in The Black Cat segment of Dario Argento/George A. Romero horror film Two Evil Eyes. A year later, she was cast in TV show Honey, I'm Home which was cancelled after two seasons.
After graduating from high school, Benz enrolled in New York University to study acting. After graduating from there , she moved to Los Angeles where she was offered a bit part in a 1994 episode of Married... With Children. Her other TV roles included Boy Meets World, Diagnosis Murder, and The Single Guy.
In 1996, Benz auditioned for the lead role for upcoming TV series Buffy the Vampire Slayer, but lost out to Sarah Michelle Gellar. However she was offered the small role of Darla, a vampire who had the first line in the show's run. She appeared in more TV roles including The Big Easy and Fame L.A. She made two movies, dark comedy Jawbreaker and Dirt Merchant. The first season of Roswell saw Benz play undercover FBI agent Kathleen Topolsky.
Benz reprised her role of Darla for TV series Angel in 2000, appearing in at least one episode every season. She appeared as Ursula in the film George of the Jungle 2. Benz appeared in the series Peacemakers, Coupling, NCIS, and Oliver Beene. She landed the lead role of Annie Garrett in the Hallmark TV movie The Long Shot. Benz also provided the voice of Miranda Keyes for the video game Halo 2. She played the lead role of Danielle in Bad Girls From Valley High (a film shot in 2000 under the title A Fate Totally Worse Than Death) which was released on DVD in 2005. She had a small role in the critically acclaimed TV movie Lackawanna Blues. In the Sci-Fi Channel original film Locusts: The 8th Plague, she played the lead female role Vicky. She also appeared in the straight-to-DVD movie 8mm 2 as Lynn.
Benz appeared in episodes of Supernatural, CSI: Miami, Law & Order, and CSI: Crime Scene Investigation. She had a supporting role in a Swedish independent movie called Kill Your Darlings, a lead role in the Lifetime movie Circle of Friends and joined the cast of TV show Dexter as Rita Bennett. Benz played a lead role in the fifth film of the popular horror franchise, Saw V, as Brit, a real-estate developer who is one of Jigsaw's five victims. She had a supporting role in Punisher: War Zone as Angela. Benz starred with in 2008's Rambo, the fourth film of that series.
She plays the title role in the short film Kidnapping Caitlynn, which premiered at the Vail Film Festival 2009. That same year, she starred in the Lifetime movie Held Hostage as Michelle Estey. She also starred in the Hallmark Channel movie Uncorked as Johnny Prentiss. She is the lead female character Special Agent Eunice Bloom in The Boondock Saints II: All Saints Day. She has been cast in another independent film called Bedrooms as Anna. She plays Frankie in the movie Answers to Nothing.
Benz appeared on The Soup with Joel McHale. She next took a recurring role on Desperate Housewives as Robin Gallagher, a stripper with a heart of gold and a Masters degree in education who gets offered the chance to transition into a more legitimate career. After the season 4 finale of Dexter, Benz returned for the season 5 premiere.
In early 2010, ABC announced that Benz had landed a lead role as Stephanie Powell, in the network's drama pilot No Ordinary Family. Production of the series commenced the following May and it premiered on September 28, 2010, as part of the 2010–11 season. On May 13, 2011, No Ordinary Family was canceled after one season with only twenty episodes filmed. In 2011, she was cast in the new CBS TV show A Gifted Man. She was originally a co-star but was downgraded to recurring. A Gifted Man was canceled by CBS in May 2012 after one season of 16 episodes.
She will also be starring in TV movie Ricochet as Elise Laird. Benz plays the lead female role, Mayor Amanda Rosewater, in the new science fiction series Defiance and also stars in the upcoming indie movie Supremacy and the unaired TV pilot Middle Ages.
Benz originally auditioned for the role of Buffy Summers; she described: "I was one of, like, a million girls that went in for it. I wasn't right for the role. I mean, I was five years too old. [Joss Whedon] offered me 'Vampire Girl, Number One' — she didn't even have a name. Then Darla kinda evolved on set as we were filming." She went on portraying the vampire Darla in the following episodes:
- Buffy the Vampire Slayer pilot
- "Welcome to the Hellmouth"
- "The Harvest"
- "Becoming, Part One"
- "The Prodigal"
- "Five by Five"
- "To Shanshu in L.A."
- "First Impressions"
- "Dear Boy"
- "Fool for Love"
- "The Trial"
- "That Vision-Thing"
- "Inside Out"
- "The Girl in Question"
Benz also appeared in the following featurettes:
- "A Buffy Bestiary"
- "Beauty and the Beasts: Behind Buffy's Makeup"
- "Angel Season 2 Overview"
- "The Sets of Angel"
- "The Make-Up of Angel"
- "Angel Season 3 Overview"
- "Darla: Deliver Us From Evil"
- "From Page to Screen"
- "Buffy Wraps"
- "It's Always Been About the Fans"
- "Halos & Horns: Recurring Villainy"
- Julie Benz on Wikipedia
- "Julie Benz On The Difficulties Of A 'Buffy' Revival, Her Shocking 'Dexter' Exit & More". theMusic.com.au, June 9, 2017.