The grandson of Broadway actor George Bratt and the son of a Peruvian mother dedicated to the Native American cause, Bratt grew up in Northern California but did not get the acting bug until he attended college. Cast in his first TV gig while studying at the American Conservatory Theatre in San Francisco, he abandoned pursuing a masters degree to act full-time. His first two pilots, "Juarez" and "Lovers, Partners & Spies" did not sell, but he was on the air full-time in the short-lived "Knightwatch" (ABC, 1988), portraying an ex-gang leader who had become the leader of a youthful anti-crime patrol loosely based on NYC's Guardian Angels. He followed with another short-lived series, NBC's "Nasty Boys" (1990), executive produced by Dick Wolf, who also created and executive produced "Law & Order", and though Bratt had resisted all attempts by Wolf to get him to guest star on that series, he could not resist the offer of a regular role.

Prior to "Law & Order", Bratt's feature work consisted of supporting roles, usually as Latinos or Native Americans. Following his debut in "Bright Angel", he appeared in "Chains of Gold" (both 1990), portraying a vicious drug dealer who kept young Joey Lawrence in a cage in order to lure hero John Travolta to his den. He raised his profile further with roles in "One Good Cop" (1991), "Bound by Honor" and "Demolition Man" (both 1993) before grabbing Hollywood's attention with two 1994 releases: "The River Wild", in which he portrayed a Native American ranger doomed for his attempt to help Meryl Streep; and "Clear and Present Danger", as the field officer for American soldiers sent by the CIA to infiltrate the Colombian countryside. The increased exposure led to a lead in the ABC miniseries "James A. Michener's Texas" (1995), and he developed his role as the proud, impatient Mexican Benito Garza as far as the subject material allowed.

Although Bratt portrayed the conservative Curtis on "Law & Order", in keeping with his upbringing, his own politics were left of center, and he remained active in Native American concerns, including yearly involvement in the American Indian Friendship House in Oakland, California. He starred in and helped produce "Follow Me Home" (1997), a low-budget film directed by his brother, Peter Bratt, and then parlayed his "Pretty Man" good looks into capturing the heart of Hollywood's quintessential "Pretty Woman", Julia Roberts, whose guest-starring turn in the 200th episode of "Law & Order" elicited tremendous ratings. Since leaving the show, Bratt delivered the necessary charm as part of the interesting triangle of "The Next Best Thing" (2000), acting alongside Madonna and Rupert Everett. He also starred that year in "Red Planet", about a planned colony on Mars.

In the spring of 2001, Bratt's relationship with Julia Roberts ended, amid a flurry of media scrutiny. After being her loyal companion at the 2001 Oscars where Roberts took home the Best Actress award, everyone wanted to know what went wrong with Hollywood's dark-eyed darling couple. While remaining expectedly ambivalent about the break-up ("I've moved on"), Bratt hinted that Roberts's fame put him too much in the spotlight. Other sources said Bratt was just looking to marry and start a family, and Roberts was not on the same page. Soon after his parting with Roberts, however, Bratt's career began to pick up steam. He was cast as the lead in two high profile features, "Abandon" (2002), opposite Katie Holmes, and "The Great Raid" (filmed in 2002). With these big screen appearances, Bratt was poised to really come into his own as a powerful leading-man star. His personal life fell into place too; he married longtime acquaintance Talisa Soto in May of 2002 and announced soon after that Soto was pregnant.

His next high-profile film appearance was in the lackluster comic book spin-off "Catwoman" (2004), in which he played a detective who becomes the love interest of both the Feline Fatale and her mousy alter-ego (Halle Berry)—despite the film's many weaknesses, Bratt demonstrated a healthy dose of leading man charm and an enviable lack of ego, allowing himself to be physically dominated on screen by Berry and villainous Sharon Stone. In August 2005, “The Great Raid” was finally released after two years on the Miramax shelves. Bratt played Colonel Henry Mucci, commander of the 6th Ranger Battalion that went 30 miles behind Japanese lines to rescue 500 POWs from the notorious Cabanatuan prison camp during World War II. Though Bratt exuded the requisite macho bravura, his characterization of a tough guy prone to brooding by staring off into the distance while smoking his pipe lacked depth, nuance and—above all—humor.