Dawson made the most of her opportunity in "Kids" and pursued an acting career. Her next major role was that of Lala in Spike Lee's "He Got Game" (1998). Here she played a bewitching but opportunistic girlfriend to uncommonly talented basketball player Jesus (Ray Allen), eager to get her share of his potential fame and wealth. Dawson could also be seen that year in the episodic comedy "Side Streets", playing a Puerto Rican Bronx native with relationship problems in this New York City-set feature looking at people in each of the city's five boroughs. In 1999, Dawson teamed up with Prince for his timely re-release of his 1980s hit "1999". This remixed version featured the actress in an introductory voiceover, offering commentary on the state of the world in the titular year. Later in 1999, she was featured in the New York City high school hostage drama "Light It Up", playing a brainy, cool-headed student encouraging moderation in the explosive situation. 2000 saw her with a supporting role as flaky party girl Lana in the disappointing romantic comedy "Down to You".

Dawson's career was certainly on the ascent. She landed a co-starring role in the Edward Burns romantic comedy "Sidewalks of New York" (2000) and was also cast as Valerie in the live-action adaptation of "Josie and the Pussycats" (2001). In 2002, Dawson was involved in saving the world in the summer sequel hit "Men In Black II". She replaced Halle Berry as the female lead of the long-delayed futuristic comedy "The Adventures of Pluto Nash" opposite Eddie Murphy and ended the year co-starring in Spike Lee's crime drama "The 25th Hour." Her most commercial role to date came when she was cast alongside The Rock and Seann William Scott in the crowd-pleasing action-comedy-buddy flick "The Rundown" (2003), serving as the love interest for the stars' combative characters, and the actress's fiery depiction of Alexander the Great's hellcat wife Roxanne (and her erotic if violently charged nude scenes) were among the best elements of Oliver Stone's bloated would-be epic "Alexander" (2004).

As the neice of a professional cartoonist, Dawson was naturally drawn to appear in director Robert Rodriguez and writer-artist Frank Miller's visually arresting adaptation of Miller's crime noir comic book series "Sin City" (2005), playing the dominatrix prostitute/"warrior woman" Gail in "The Big Fat Kill" sequence, gleefully mowing down the enemies of Old Town's hookers with automatic weapons while still looking fabulous in lingerie. She then had an arresting, carnally charged turn as the alluring but heroin-addicted dancer Mimi Marquez in the 2005 big screen adaptation of the smash Broadway musical "Rent," revealing a terrific aptitude for song and dance. Although the film's cast was populated by many of the stage play's original players, Dawson stole scenes from them all with her canny ability to attract on camera.