Williams served on the USS Sampson during the U.S. invasion of Grenada. His awards include the Armed Forces Expeditionary Medal, two Navy Expeditionary Medals, two Humanitarian Service Medals, a Navy Achievement Medal, two Navy Commendation Medals and two Meritorious Service Medals. After 12 years of military service he departed as a Lieutenant Commander in the Navy.
Williams also guest-starred in episodic television and off-Broadway plays. Among others, he portrayed a Navy SEAL lieutenant in several episodes of the television series JAG. Williams also produced and starred in a short-lived television series called Matt Waters, which appeared on CBS in 1996. He played an ex-Navy SEAL turned inner-city high school teacher.
Williams played the judge presiding over Erica Kane's (Susan Lucci) murder trial on the ABC soap opera All My Children in 2002. In 2003 Williams made a guest appearance on the soap as himself, to promote an episode of his own show on which several AMC stars were scheduled to appear. In 2004 he hosted American Candidate, a political reality show for Showtime.
On January 30, 2008, Variety reported that CBS TV Distribution terminated The Montel Williams Show when key Fox-owned stations chose not to renew it for the 2008-2009 season. This followed an appearance on the show Fox & Friends in which he criticized the media's lack of coverage on the Iraq War, and took the hosts to task for their (and the media in general) excessive coverage of the death of actor Heath Ledger, contrasted with the sparse coverage of U.S. soldiers dying in Iraq.
On May 16, 2008 the last episode of The Montel Williams Show aired.
Williams participated in the 2007 World Series of Poker main event, and planned to donate any potential winnings to families affected by the Iraq war. He was eliminated in Day 2. During the event Williams also spoke out about the port security bill signed in 2006 that banned on-line gaming sites from accepting money transactions from the U.S. In August 2007, Williams was initiated as an honorary member to Phi Beta Sigma Fraternity.
Williams was diagnosed with Multiple Sclerosis in 1999 and now heads the Montel Williams MS Foundation.
On November 30, 2007, while in Savannah, Georgia to promote PPA, Montel Williams threatened reporters following an earlier interview at which a 17-year-old high school intern reporter (Courtney Scott) for the Savannah Morning News had asked him a question about whether restriction of pharmaceutical profits would discourage research and development of new drugs. Angered by the question, Williams subsequently terminated that videotaped interview.
Williams' public relations representatives later apologized for his hostile outburst in an issued statement, "I mistakenly thought the reporter and photographer in question were at the hotel to confront me about some earlier comments. I was wrong, and I apologize for my overreaction."