Fitzwater was born on a farm in Salina, Kansas. He graduated from Kansas State University in 1965 with a degree in journalism. While in school, he worked at newspapers in various Kansas communities before moving to Washington, DC upon graduation. He also served in the United States Air National Guard. Fitzwater is also a member of Delta Tau Delta Fraternity.
In Washington, Fitzwater served at various Federal agencies, including the Appalachian Regional Commission (1965–67), the U.S. Department of Transportation (1970–72) and the Environmental Protection Agency (1972–81). He served as Deputy Assistant Secretary for Public affairs at the Department of the Treasury from 1981 to 1982.
Fitzwater headed to the White House in 1983, serving as Special Assistant to the President and Deputy Press Secretary for Domestic Affairs. He served as Vice President Bush's Press Secretary from 1985 to 1987.
When James Brady was shot in the assassination attempt on President Reagan in 1981, he was unable to return to work, though he retained the title of Press Secretary for the duration of Reagan's term. Others served under the title of "Assistant to the President for Press Relations"
In January 1987, Reagan made Fitzwater the Acting Press Secretary under the title of "Assistant to the President for Press Relations". He served in this capacity until Reagan left office in 1989.
When Mikhail Gorbachev first visited the United States, in Reagan's first term, Fitzwater gave joint press briefings with his Soviet counterpart. Over 7,000 journalists attended them.
When George H.W. Bush took over as president in 1989, Fitzwater was again tapped to be the presidential spokesman, this time with the title of Press Secretary.
Fitzwater received the Presidential Citizens Medal in 1992. He has worked on the television show The West Wing as a consultant. In 2002, Franklin Pierce University in Rindge, New Hampshire completed the Marlin Fitzwater Center for Communication in his honor.
In 2002, Fitzwater was interviewed by Ali G on Da Ali G Show where he (Fitzwater) became visibly hostile to the line of questioning, particularly when he was asked questions about Hillary Clinton's sexual orientation. He terminated the interview early and referred to him as "an idiot." Fitzwater later recalled that he had his doubts about conducting the interview after seeing Ali G, but thought that his gangsta rap appearance was simply appealing to his "hippie" audience. After the interview, he said he was "two steps away from calling the sheriff."
Fitzwater married Melinda Andrews in 1999. He has two children, Bradley and Courtney. He lives in a private community called Rest Haven in Deale, Maryland, a village on the Chesapeake Bay. Fitzwater was profiled on Retirement Living TV and on a web feature Talk2 on RL.TV talking about his career in Washington with John Palmer.