Mourning—a centre 6 feet 10 inches (2.08 metres) tall—played collegiate basketball at Georgetown University, in Washington, D.C. He was the second overall pick in the 1992 NBA draft by the Charlotte Hornets, and he spent three seasons with the team before being traded to the Heat. A seven-time NBA All-Star, he was named the league's Defensive Player of the Year in 1999 and 2000 and earned first team All-NBA honours in 1999. He won gold medals with the U.S. team at the 1994 world championships and at the 2000 Olympic Games in Sydney.

Shortly after the Olympics, he was diagnosed with focal glomerulosclerosis, a disease that affects the filtering process of the kidneys. Mourning played in only 13 games the following season but recovered to make the NBA Eastern Conference All-Star Team in 2002. His condition worsened, however, and he sat out the 2002–03 season. As a free agent, he signed a four-year contract with the New Jersey Nets in 2003 but was forced to retire in November because of his kidney problems. He received a kidney from his cousin in December and began working toward an NBA comeback soon thereafter.

Mourning returned to the Nets for the 2004–05 season and was subsequently traded to the Toronto Raptors, but he refused to report to the team. After a buyout that again allowed him to become a free agent, he re-signed with the Heat in March 2005. He played limited minutes in his second stint with the Heat but was a valuable reserve as Miami advanced to the 2006 NBA finals. Mourning had his best game of the play-offs in the Heat's decisive game-six victory over the Dallas Mavericks, which gave Miami its first championship in franchise history. In December 2007 Mourning suffered a severe knee injury, which forced him to miss the remainder of the 2007–08 season. He retired from the NBA in January 2009.