Mobley was drafted in the first round of the 1996 NFL Draft by the Broncos after a college football career in Kutztown University. Mobley's best season was in 1997 when he had 132 tackles and four sacks and was an All-Pro that season. Mobley missed most of the 1999 season because of an injury.
Mobley suffered a bruised spinal column during the 2003 season after he collided with his teammate Kelly Herndon in a game against the Baltimore Ravens, and the injury was severe enough that the Broncos cut him before the 2004 season in order to allow him time for recovery. He later re-signed with the Broncos and retired because of the injury.
Mobley served seven days in prison for a DUI conviction in 2004 after being pulled over and arrested on December 28, 2002. He was found guilty by a jury in April 2004 and was sentenced to 365 days behind bars, but the judge in the case later reduced it to seven days.
In Super Bowl XXXII, Mobley deflected a Brett Favre pass on 4th and 6 from the 31-yard-line with just over 30 seconds left in the game. The deflection sealed a 31-24 victory for the Broncos.
During his career, Mobley played in 105 career games, starting 102 of them, including two Super Bowls, during which he made 608 career tackles, 10.5 quarterback sacks, and five interceptions for 45 yards and a touchdown.
He is the cousin of former NBA player Cuttino Mobley.