Hilliard accepted an athletic scholarship to attend the University of Florida in Gainesville, Florida, where he played wide receiver for coach Steve Spurrier's Florida Gators football team from 1994 to 1996. During his three seasons as a Gator, the team won three SEC Championships in 1994, 1995, and 1996. As a junior in 1996, he was paired with fellow Gators receiver Reidel Anthony and both posted 1,000-yard seasons, and both Hilliard and Anthony were recognized as first-team All-Southeastern Conference (SEC) selections and consensus first-team All-Americans, as the Gators won the Bowl Alliance national championship—their first-ever national football title. The Gators finished the season with a record of 12–1 after a 52–20 victory over the top-ranked Florida State Seminoles in the 1997 Sugar Bowl. Memorably, he set three Sugar Bowl records against the Seminoles: he had 150 receiving yards, including an 82-yard touchdown catch, and scored a total of three touchdowns for eighteen points.
Hilliard declared himself eligible for the NFL Draft after his junior season, and finished his college career with 126 receptions for 2,214 yards and twenty-nine touchdowns. In a 2006 series published by The Gainesville Sun, he was recognized as No. 14 among the 100 all-time greatest Gator players from the first century of Florida football. He was inducted into the University of Florida Athletic Hall of Fame as a "Gator Great" in 2009.
Hilliard signed with the Tampa Bay Buccaneers after the 2004 season. During his first two seasons with Tampa Bay, he was used mainly as a third or fourth receiver, but in 2007 he started ten games making sixty-two receptions for 722 yards. Hilliard was released by the Buccaneers on February 25, 2009. Hilliard finished his NFL career with 546 catches for 6,397 yards and thirty-five touchdowns.
In his twelve-season NFL career, Hilliard appeared in 161 regular season games, started 105 of them, and made 546 catches for 6,397 yards and thirty-five touchdowns. He also had 126 rushing yards on sixteen attempts.