Williams was born in Beckville, Texas. After high school, he signed with rural Cisco Junior College, but soon left the school. Following a year of oil field work, he decided to walk-on to Kilgore College located in the town of Kilgore, Texas. It was here that Kilgore head coach Jimmy Rieves decided to change him from a cornerback to a linebacker, and he excelled there. Williams helped lead Kilgore to an undefeated season in 2001, and a #2 national ranking. Prior to entering the NFL, Williams played for the University of Nebraska, where he completed his degree in sociology.
Williams started all 16 of the Falcons' regular-season games of the 2005 NFL season, recording 132 tackles, and ranking second on his team for that statistic. He had a career-high 15 tackles in a December 12, 2005 game against the New Orleans Saints.
On March 1, 2008, Williams signed a five-year contract with the Kansas City Chiefs. After four seasons with Chiefs, Williams was released on March 6, 2012.2
Williams signed a one-year contract with the San Diego Chargers on March 8, 2012.3
"2004 NFL Draft Listing". Pro-Football-Reference.com. Retrieved May 6, 2023. https://www.pro-football-reference.com/years/2004/draft.htm ↩
"Chiefs part ways with veteran linebacker Demorrio Williams". KCChiefs.com. Archived from the original on March 8, 2012. https://web.archive.org/web/20120308101126/http://www.kcchiefs.com/news/article-2/Chiefs-part-ways-with-veteran-linebacker-Demorrio-Williams/71dc981e-e8c4-4966-9507-d1245ed2f778 ↩
"Chargers net ILB Williams". Chargers.com. Archived from the original on March 13, 2012. Retrieved March 12, 2012. https://web.archive.org/web/20120313003255/http://www.chargers.com/news/article-1/Chargers-net-ILB-Williams/b3d80295-7d34-4ee4-b58b-677405fa82c5 ↩