Gibson earned a BA from the UCLA School of Theater, Film and Television. He began his reporting career with The Hollywood Reporter (1969-1972) and worked for Atlantic Records (1972-1974). Gibson worked for KFWB-AM (1974-1975) and KEYT-TV (1975-1977). At KCRA, he was a feature reporter on the "Weeknight" magazine show (1977-1979) and San Francisco bureau chief (1979-1989).

Beginning in 1992, Gibson worked as an NBC News correspondent in Burbank, California. In 1994, he became the first West coast correspondent for NBC News Channel. He covered the 1995 O. J. Simpson trial for the murders of Nicole Brown Simpson and Ronald Goldman for NBC News Channel and Rivera Live on CNBC. In 1996 he was named anchor for daytime programming on MSNBC, where he covered the Bill Clinton and Monica Lewinsky scandal in 1998.

Gibson joined the Fox News Channel in September 2000 as the host of its news program The Big Story. He also wrote the New York Times bestselling books The New World Sport and The War on Christmas.

On March 12, 2008, Fox News Channel announced The Big Story was being replaced with America's Election Headquarters, a program more directly geared toward following the 2008 U.S. presidential election. The Big Story was not renewed after the election and was replaced with The Glenn Beck Program in January 2009. He has been a regular guest-panelist on Fox's late-night satire show Red Eye w/ Greg Gutfeld.

In 2004 Gibson claimed that the British Broadcasting Corporation was anti-American, accusing the BBC of having "a frothing-at-the-mouth anti-Americanism that was obsessive, irrational and dishonest". Television - News - Ofcom criticises Fox News Channel - Digital Spy He also claimed that reporter Andrew Gilligan, who was covering the 2003 Iraq War for BBC Radio 4 in Baghdad, had, "insisted on air that the Iraqi Army was heroically repulsing an incompetent American military".

Gibson's criticisms were rejected by Ofcom when it investigated viewer complaints of Gibson's item. Ofcom also found that Gibson's broadcast was in violation of several UK television regulations, concluding that Gibson's commentary did not display a "respect for truth", failed to offer the BBC a chance to respond to the allegations, and was based on "false evidence."

Gibson as a commentator often attracts partisan criticism.

On The Big Story in 2006, Gibson responded to a Washington Post story which noted that the US Census reported "Nearly half of the nation's children under five are racial or ethnic minorities, and the percentage is increasing mainly because the Hispanic population is growing so rapidly." Gibson said further: "Do your duty. Make more babies... half of the kids in this country under five years old are minorities. By far the greatest number are Hispanic. You know what that means? Twenty-five years and the majority of the population is Hispanic. Why is that? Well, the Hispanics are having more kids than others. Notably the ones Hispanics call gabachos, white people, are having fewer."

Following the 2007 SuccessTech Academy shooting in Cleveland, Ohio, on his radio show Gibson commented "I knew the shooter was white. I knew he would have shot himself. Hip-hoppers don't do that. They shoot and move on to shoot again. And I could tell right away because he killed himself. Hip hoppers shooters don't do that. They shoot and move on."In a 2008 edition of his radio show, Gibson commented on actor Heath Ledger's death the day before. He opened the segment with funeral music and played a clip of the famous line "I wish I knew how to quit you" from Ledger's film Brokeback Mountain; he then said "Well, I guess he found out how to quit you." Among other remarks, Gibson called Ledger a "weirdo" with "a serious drug problem." The next day, he addressed outcry over his remarks by saying that they were in the context of jokes he had been making for months about Brokeback Mountain, and that "There's no point in passing up a good joke." Gibson later apologized on his television and radio shows.

In February 2009, Attorney General Eric Holder had given a speech to Justice Department employees as a part of the observance of Black History Month during which he described the United States as being a "nation of cowards" in its reluctance to discuss racial relations. Gibson criticized Holder's remarks as inappropriate. John Sanders, who at the time was technology reporter for WBAL-TV in Baltimore, then edited Gibson's remarks which had followed news reports of a monkey who had escaped from a Seattle zoo making it appear that Gibson had compared Holder to a monkey "with a bright blue scrotum" on Fox. Sanders then posted the altered video on youtube.com as a joke. However, the video was widely-publicized on news websites, including the Huffington Post, as if it were authentic. Sanders was fired over the video, and Gibson said that the spread of the fake video has had a "personal" impact upon him.