Phillippe's acting career began with an appearance in ABC daytime drama One Life to Live. His character Billy Douglas, whom he played from 1992 to 1993, was the first gay teenager in a daily soap opera, causing a stir. After leaving the show, Phillippe moved to Los Angeles, where he appeared in a number of small parts in various television shows and movies, including 1996s White Squall.

Phillippe was cast in the 1997 horror film, I Know What You Did Last Summer, which co-starred Sarah Michelle Gellar, Freddie Prinze, Jr. and Jennifer Love Hewitt. The film was a success in October of that year, and led to Phillippe gaining wider renown and being cast in a few more high-profile films, including 54 in 1998 and 1999's Cruel Intentions, a modern retelling of the Choderlos de Laclos' novel, Les Liaisons Dangereuses. The latter film, which also starred Phillippe's future wife, Reese Witherspoon, as well as his I Know What You Did Last Summer co-star, Sarah Michelle Gellar, was a succ