Moss attended the University of Miami, and joined the Miami Hurricanes football team in 1997 as a walk-on, before being awarded a scholarship after the season’s third game. He went on to break the Hurricanes’ record (previously held by Michael Irvin) for most receiving yards (with 2,546 yards). He finished his 2000 senior season with 1,604 all-purpose yards, received first-team All-Big East Conference honors, and was recognized a consensus first-team All-American. Moss also became the first player to earn Big East Offensive Player of the Year and Special Teams Player of the Year honors in the same season.

Moss was a first round (16th overall) pick in the 2001 NFL Draft by the New York Jets out of the University of Miami.

In the 2001 season, Moss made his NFL debut in Week 10 against the Miami Dolphins. Moss made his first career catch in Week 12 against the New England Patriots.

In the 2002 season, Moss made his first career start in Week 1 against the Buffalo Bills.

Following the 2004 season, Moss was acquired by the Washington Redskins in a trade with the New York Jets for Laveranues Coles. Moss signed a six-year contract with the Redskins on May 4, 2005.

His 2005 season with the Redskins was the best in his professional career, with 84 receptions for 1,483 yards (second highest in the NFL that year, behind only Steve Smith of the Carolina Panthers), setting a new Redskins single-season receiving record, and nine touchdowns. In 2005, Moss also was selected to his first NFL Pro Bowl. Moss recorded 18 rushing yards and 3 catches for 39 receiving yards at the Pro Bowl.

In the first three games of the 2006 season, he recorded only 13 catches for 188 yards. On October 1, 2006, however, Moss exploded for a season-high 138 yards on 4 catches, hauling in two touchdowns of 55 and 8 yards, as well as a 68-yard game-winning touchdown to give Washington the victory in overtime over the visiting Jacksonville Jaguars 36–30. Due to injuries that kept him inactive much of the year and less than 100% when he did play, Moss finished the 2006 season with 790 yards and 6 touchdowns on 55 receptions.

In the 2007 season, Moss started and played in 14 games and recorded 61 receptions, 808 receiving yards, and three touchdowns.

In the 2008 season, Moss recorded over 1,000 receiving yards for the third time in his career.

In 2008 married Latosha Moss. They have four children together

Starting in all 16 games in 2009, Moss recorded 70 receptions, 902 receiving yards, and three touchdowns.

In the 2010 season, the last season of his contract with the Redskins, Moss recorded 1,115 receiving yards making this the fourth time in his career that he recorded over 1,000 receiving yards. He achieved a new career high of 93 receptions to go along with six touchdowns in the 2010 season.

In May 2010, The Washington Post reported that Moss allegedly received human growth hormones from doctor Anthony Galea.

Moss is an important figure in Miami Hurricanes football history, generally considered (along with Irvin) to be one of the most accomplished wide receivers in the university’s history. He graduated as the school’s all-time leader in receiving yards (2,546), punt return yards (1,196), and all-purpose yards (4,394). Moss was interviewed about his time at the University of Miami for the documentary The U, which premiered December 12, 2009 on ESPN. He was inducted into the University of Miami Sports Hall of Fame in 2011.

With his original contract ending, Moss re-signed with the Redskins. On July 26, the Redskins signed him to a three-year, $15 million contract that included a $5 million signing bonus. He was made offensive co-captain along with Trent Williams. In Week 7 against the Carolina Panthers, Moss suffered a broken left hand. He made his return to the field in Week 12 against the Seattle Seahawks. In Week 14 against the New England Patriots, Moss caught a 49-yard touchdown pass from wide receiver Brandon Banks, the first passing touchdown of Banks’ career. Working mostly out of the slot receiver position, Moss played and started 12 games and recorded 46 receptions, 584 receiving yards, and four touchdowns in the 2011 season.

During the 2013 offseason, Moss restructured his contract in order to clear up cap space. After the Week 11 game against the Philadelphia Eagles, he surpassed 10,000 career receiving yards making him the seventh active player at that time to reach this milestone along with Tony Gonzalez, Reggie Wayne, Andre Johnson, Steve Smith, Larry Fitzgerald, and Anquan Boldin.

Set to become a free agent for 2014, Moss re-signed on a one-year deal to remain with the Redskins on March 11, 2014.

During a Redskins-Giants game on December 14, 2014, a touchdown in the closing seconds of the first half by quarterback Robert Griffin III was overturned by official Jeff Triplette after he saw that Griffin had fumbled the ball in the end zone. Moss angrily confronted Triplette and the officiating crew as they walked back to the locker room. An unsportsmanlike conduct penalty was assessed against Moss, and he was also ejected from the game, for which he heavily protested.

In 2016, Moss earned a Master of Business Administration degree from the University of Miami Business School.

In March 2017, it was announced that Moss would be a color commentator for the Washington Valor of the Arena Football League.