In 1997, Griffith joined the Denver Broncos, and played five seasons for the Broncos primarily as a blocking back for Terrell Davis. He didn't get very many rushing attempts, but was often used as a receiver out of the backfield, recording 27 receptions in 1996 and 26 in 1999. With the Broncos, Griffith won two Super Bowl rings in Super Bowl XXXII and Super Bowl XXXIII. Griffith was a big contributor in the Broncos Super Bowl XXXIII win, scoring two rushing touchdowns in the game. He also made a key 23-yard reception in the final quarter of Super Bowl XXXII, setting up Denver's final touchdown of the game. While playing for the Broncos, Howard earned the nickname "The Human Plow" due to his successful blocking for Davis.
Griffith retired from the NFL at the start of the 2002 season, due to a neck injury sustained in the 2001 preseason that caused him to miss the entire 2001 campaign. His final totals over his 11 NFL seasons include 351 rushing yards and three touchdowns, along with 122 receptions for 844 yards and nine touchdowns.
Today, Griffith works as a football analyst. He is one of the lead in-studio analysts for the Big Ten Network, giving his weekly analysis of the NFL. In 2005, he was an analyst for the NFL and NFL Europe football leagues, as he commentated games that were broadcast by Fox and the NFL Networks. He is the author of the 2001 book Laying it on the Line.