Barrett was subsequently cast in a regular role on NBC's "Wind on Water,” marking her network series debut. While the surf-loving actress proved a natural for this beach-set series, low ratings led to its early demise. Later that same year, she had a guest role on the UPN series "Guys Like Us", starring her boyfriend and fellow MTV series vet, former "Singled Out" host Chris Hardwick. In 1999 the actress guest starred on an episode of Fox's acclaimed sci-fi series "Millennium" and had a recurring role as the fetching older woman who takes a liking to awkward Duncan (David Moscow) after seeing through the facade of womanizer Jack (David Rosenbaum) on The WB's teen sitcom "Zoe, Duncan, Jack and Jane" (1999). When the series returned from hiatus in 2000, revamped as the college-age sitcom "Zoe...", Barrett had been dropped from the cast, but soon reemerged on the network as a regular on the midseason drama "D.C." (2000) playing the impulsive and ambitious Finley Scott, a young woman who ditches graduate school and heads to the nation's capital to pursue her dreams. She added another short-lived political-minded drama to her resume, appearing as one of James Cromwell's three daughters in "Citizen Baines" (CBS, 2001).

In addition to her modeling and television credits, Barrett began an entry into film with a featured role in the independent horror thriller "Campfire Tales" (1998). She honed her craft in indie fare while occasionally landing higher-profile gigs in films such as "Urban Legend: Final Cut" (2000) and the Sam Shepherd-penned telepic "See You In My Dreams" (2000). Barrett's film career took a quantum leap forward when she was cast by director Robert Benton in his adaptation of Phillip Roth's bestseller "The Human Stain" (2003). In a flashback sequence, Barrett delivered a touching performance as Steena Paulsson, the unsuspecting blonde, Midwestern girlfriend of young Coleman Silk, a man of mixed race passing as white, whose revelation to Steena is both surprising, cowardly and cruel. With her star on the rise, Barrett next garnered starring roles in high visibility projects, including the firefighting drama "Ladder 49" (2004) as Joaquin Phoenix's love interest, and the comedy sequel "Bridget Jones: The Edge of Reason" (2004).

Barrett continued her climb up the Hollywood food chain when she was cast in the larger-than-life remake, “Poseidon” (2006), playing a young mother struggling to escape a capsized ocean liner with a ragtag group of passengers who must rely on and trust one another despite their differences. She next costarred in “The Last Kiss” (2006), Tony Goldwyn’s remake of the Italian film “L’Ultimo Bacio” (2001), a romantic drama about a late 20-something (Zach Braff) struggling with a before-30 crisis and the impending birth of his first child with his girlfriend (Barrett), leading him to embark on an affair with a college student (Rachel Bilson) he meets at a wedding. Then in “School for Scoundrels” (2006), Barrett was the long-time object of desire for a meter maid (Jon Heder) plagued by anxiety and low self-esteem who enrolls in a top secret confidence building class run by the suave, but underhanded Mr. P (Billy Bob Thornton), an unorthodox and competitive life coach determined to get results even if it means destroying the lives of his students.