While modeling in Italy, Larter met fellow model and aspiring actress Amy Smart and the two “became instant friends”, according to Larter. In November 1996, Larter portrayed fictional actress Allegra Coleman in an Esquire magazine hoax. When speaking about the cover and her subsequent fame, Larter said, “When the door opens for you in Hollywood, you need to run with it. You know?” Larter is currently signed to IMG Models.

Larter landed her first professional acting roles in 1997 when she appeared in several television programs. She appeared in an episode of the Brooke Shields television series Suddenly Susan, and the short-lived series Chicago Sons. These roles were followed by a number of other appearances on Dawson’s Creek, Chicago Hope, and Just Shoot Me!

In 1999, Larter made her film debut in the coming-of-age dramedy Varsity Blues, which re-united her with Dawson’s Creek star James Van Der Beek and close friend Amy Smart. Smart had persuaded Larter to audition for the movie, in which she played Darcy Sears, a love interest for one of the main characters. Varsity Blues drew a domestic box office gross of US$53 million. Also in 1999, she made supporting appearances in the teen comedies Giving It Up and Drive Me Crazy, and starred in the remake House on Haunted Hill which was made for around US$20 million. The horror film, following a group of strangers invited to a party at an abandoned asylum, was panned by critics, but grossed US$15 million on its opening weekend and went on to earn over US$40 million overall.

Larter starred as Clear Rivers, one of the main characters in the teen supernatural horror film Final Destination (2000). Also starring Devon Sawa and Kerr Smith, the movie’s premise followed several teenagers who survive a plane crash but are stalked and killed by death itself. Final Destination made US$112 million by the end of its theatrical run. In 2001, she appeared in the comedy Legally Blonde with Reese Witherspoon. She played Brooke Taylor Windham, a widow accused of her husband’s murder. The film earned the top spot with US$20 million in its opening weekend and ended up grossing $141 million worldwide. With US$96 million of it total gross deriving from domestic markets, Legally Blonde is Larter’s highest-grossing film domestically.

Larter next appeared as Zerelda Mimms in the western comedy American Outlaws. Directed by Les Mayfield and co-starring Colin Farrell and Scott Caan, the movie was poorly received by critics and at the box office, garnering US$13 million at the end of its theatrical run. She also starred in Kevin Smith’s Jay and Silent Bob Strike Back. That year, Larter appeared on the cover of Maxim magazine and performed in the stage play The Vagina Monologues in New York City. In Spring 2002, Larter moved from Los Angeles to New York. “I was too young and impressionable to handle the pressures of L.A.” Larter recalled in an interview, “I’m a woman now. I am no longer the little girl who could be easily influenced.”

In 2002, Larter ranked #40 in Stuff magazine’s “102 Sexiest Women in the World”. She was listed as #49, #19 and #91 in FHM’s “100 Sexiest Women in the World” in 2007, 2008 and 2009 respectively. Maxim also ranked her #6 in their Hot 100 for 2007 and #92 in 2008. In 2008, AskMen.com featured her as #92 on the “100 Most Desirable Women in the World”. Also ranking #2 on Maxim’s “Hottest Women of Horror Movies” list, Larter has been acknowledged as a Scream queen by MSN due to her appearances in horror/thriller films. After the success of Heroes, Larter appeared on People’s “Ten Best Dressed List” as “The Newcomer” in 2007. Victoria’s Secret also acknowledged her in their list, naming her Sexiest Legs of 2008. In 2009, Larter was named Cosmopolitan magazine’s Fun Fearless Female of the year at a ceremony held in Beverly Hills.

During her time as a model, Larter moved to Los Angeles to pursue acting. In 2002, she moved to New York for a period of three years. In an interview with Phillymag, Larter gave reason for the move:

Larter has appeared on the cover of numerous magazines, including Cosmopolitan (France, Indonesia, Ecuador, Germany, Greece, Turkey and U.S.), Glamour, Health, Seventeen, Self, Shape, Maxim, Esquire, Lucky, Allure and Philadelphia Style. She has appeared in print ads and commercials throughout her career. In 2004, she appeared in print ads for Estee Lauder cosmetics. She has appeared in commercials for Parfums de Coeur Designer Imposter Body Sprays and Stolichnaya vodka. In 2010, Larter appeared as the title character in a short film for Absolut Vodka entitled “Lemon Drop”. In June of the same year, Larter was one of thousands of delegates from 130 countries who participated in a United Nations conference, ‘Women Deliver’ in Washington, D.C.. Larter, along with her husband Hayes MacArthur, hosted The Art of Elysium Gala in 2013 and are to be recipients of the Spirit of Elysium Award at the January 2014 ceremony.

Her first project there was to reprise her role as Clear Rivers in the sequel to Final Destination entitled Final Destination 2. In an interview with IGN, Larter explained her return to the franchise: “When New Line asked me to come back, I thought it was great. They showed me the script and let me have some input, and it was really terrific.” The film made US$90 million worldwide, to a mixed critical reception. A year later, Larter served as an associate producer of and starred in the thriller Three Way, and in 2005, she appeared in the independent political thriller Confess, and had a role in the romantic comedy A Lot Like Love, starring Amanda Peet and Ashton Kutcher.

Larter moved back to Los Angeles in 2005. Her first audition was for the NBC science fiction drama television series Heroes. Larter played the characters of Niki Sanders, who suffered from DID, and Tracy Strauss on the show created by Tim Kring. Larter’s initial character Niki Sanders, was a wife, mother, and a former internet stripper from Las Vegas who exhibits superhuman strength and alternate personalities who go by the names of Jessica and Niki. “Ali read for the part and just owned it from the second she walked in,” Kring said to the Chicago Tribune, “It was a very impressive audition.” As of the third season, Larter began to play the new character of Tracy Strauss, who possessed the ability to freeze objects; and later, turn her body into water.

In January 2005, she moved to Los Angeles for a role in Heroes. In December 2007, Larter and her then longtime boyfriend, Hayes MacArthur, were engaged to marry. They had met on the set of National Lampoon’s Homo Erectus. In a 2007 interview with Cosmo, Larter said “I told my boyfriend after three weeks that I wanted to marry him and that we could do it tomorrow.” On August 1, 2009, Larter married MacArthur in an intimate outdoor ceremony which took place at MacArthur’s parent’s estate in Kennebunkport, Maine. During the ceremony, guests arrived via trolleys to the sounds of Irish music playing in honor of MacArthur’s heritage; among the invited was Larter’s close friend Amy Smart. The couple later purchased a three-story home in the Hollywood Hills for $2.9 million. On July 20, 2010, Larter announced that she and MacArthur were expecting their first child and later, on the September 10 episode of Late Night with Jimmy Fallon, announced that she was expecting a boy. Larter admitted that she and MacArthur left the country for Europe in an effort to hide the news of the pregnancy. Larter gave birth to the couple’s son, Theodore Hayes MacArthur, on December 20, 2010. In August 2014, Larter confirmed that she and MacArthur were expecting their second child that winter. She gave birth to her second child, a girl named Vivienne Margaret on January 15, 2015. Larter has two dogs, Jackpot and Ella.

Larter took on the title role in Marigold (2007), alongside Salman Khan. The film was released in August 2007 and revolved around an American actress (Larter) who goes to India and gets caught up in the exotic world of Bollywood. Filming took place in North India and London, commencing in June 2004. In an interview with the BBC, Larter remarked this role was “an opportunity to overcome my fear of singing and dancing because I have no professional training […] I really focused on the character and loved this journey she went on and the experiences she had.” She was paid a seven-figure salary for her part in the film.

In 2007, she appeared opposite Milla Jovovich in Resident Evil: Extinction, portraying the character of Claire Redfield, who in the film, is the leader of a convoy of zombie apocalypse survivors who go to Alaska in search of a safe haven. Her role sent her to Mexicali, Mexico for filming from May to late July, and required her hair to be dyed a light red. Larter explained her character Claire: “She became the leader of this convoy. She’s incredibly strong, patient. I think she serves a role for everyone within this convoy, let it be a mother to someone, a buddy, a best friend.” Despite negative reviews, the film made a total of US$147 million worldwide. Also in the same year, she appeared with Hayes McArthur in the comedy Homo Erectus and appeared as Evelyn Garland in the biographical drama Crazy, based on guitarist Hank Garland.

Larter appeared in Glamour along with fellow actresses Rachel Bilson and Diane Lane in 2007. When asked if she still wishes she had the same body she had at 20 she replied, “No. I actually think I look better now because I feel so much better about myself now. And that’s what’s so exciting. As you get older, you get better…. Look at all these incredible women, like Vanessa Redgrave, who are still so beautiful. The reason is because they embrace who they are.” She has appeared on the covers of Shape, Cosmopolitan, Allure, Glamour, Lucky, InStyle, Maxim, and Entertainment Weekly.

Larter is often recognized for her looks. She was featured at number 39 in Maxim’s “Hot 100 of 2002” supplement and ranked at number 40 in Stuff magazine’s “102 Sexiest Women in the World”. Larter was ranked at number 6 on Maxim’s “Hot 100 of 2007” list. In 2008, she was ranked at number 92 on AskMen’s “100 Most Desirable Women in the World.”

In September 2013, Larter released her first cookbook entitled Kitchen Revelry: A Year of Festive Menus from My Home to Yours. The book was published by St. Martin’s Press. Speaking at the Aspen Culinary Festival to The Hollywood Reporter, Larter said:

While speaking to Vanity Fair at the premiere of her film Obsessed, Larter spoke about her own obsessions, “I love to cook. I spend weekends reading cookbooks—it’s really my relaxation.” She has ranked Scarface, The Bourne Identity, Best in Show, Blue Sky and Grey Gardens as her favorite films. Speaking to People in 2013 about her transition from actress to author, Larter explained:

In 2014, Larter obtained a regular part in the first season of TNT’s drama series Legends, appearing as Crystal Quest, an operative with the FBI’s Deep Cover Operations. Larter starred in the supernatural thriller The Diabolical (2015), as Madison, a single mother who battles evil forces in her house. Distributed for a VOD and limited release in certain parts of United States only, the film received largely mixed reviews; Gary Goldstein of Los Angeles Times felt that her “fraught, more seemingly complex [character] remains underdeveloped” in what he described as a “weak horror-thriller”.