He is a member of the International Council, chaired by Dr. Henry Kissinger, at the CSIS, a bipartisan Washington, D.C., think tank focused on national security and foreign affairs. Ruddy also served as a representative on the U.S. delegation headed by Senators Joseph Lieberman and Lindsey Graham to the NATO 44th Munich Security Conference.

Ruddy grew up on Long Island, New York, where his father was a decorated police officer in Nassau County. He graduated from Chaminade High School in Mineola, New York before graduating summa cum laude with a degree in history from St. John's University, New York in 1987. He earned a master's degree in public policy from the London School of Economics and also studied at the Hebrew University of Jerusalem. He worked briefly as a bilingual high school social studies Teacher in the Bronx, New York. Ruddy holds an Honorary Doctorate of Letters from St. John's University.

Ruddy then moved to the New York Post, which he joined as an investigative reporter late in the summer of 1993. After initially writing about abuse of Social Security disability benefits, he focused on the Whitewater scandal involving then-president Bill Clinton.

New York Post Editor Eric Breindel recommended Ruddy for a job at the Pittsburgh Tribune-Review owned by Richard Mellon Scaife. In November 1994, Ruddy was hired to investigate the story full-time by the Tribune-Review. In between Ruddy's departure from the Post and joining the Tribune-Review, he put out a report through the Western Journalism Center criticizing the Fiske investigation as inadequate. With the help of Scaife, the Center took out full-page ads in major newspapers to promote the report (Scaife gave $330,000 to the Center in 1994–95 before ending his support).

In 1995 he joined the Pittsburgh Tribune-Review as a national correspondent covering the Clinton White House and other stories.

Since 1996, Ruddy has been Media Fellow at the Hoover Institution on War, Revolution and Peace at Stanford University. Ruddy serves on the board of Directors of the Financial Publishers Association (FIPA), an industry trade group whose goal is "to share knowledge of best Business practices to help our members' publications grow and prosper, while empowering readers with unbiased, independent information".

Ruddy is one of (and perhaps the most prominent among) several individuals who have discussed (e.g. Morton, Robert and Ruddy, Christopher (November 22, 1997). C-Span:Book Discussion On (video). Maison Blanche Restaurant Washington, DC. ) questions regarding the death of White House counsel Vince Foster, work which was described by Former FBI Director william S. Sessions as "serious and compelling".

Newsmax Media started in 1998 when, impressed with the way news of the Clinton impeachment circulated on the Internet, Ruddy decided to start an Internet news company. With financial support from Investors, Ruddy founded Newsmax Media. The NewsMax.com website launched on September 16, 1998, with Ruddy serving as columnist and editor-in-chief. In addition to the web site, the company publishes a monthly magazine, also called Newsmax. After starting Newsmax, Ruddy was featured in a January 1999 Newsweek cover story as one of twenty "Stars of the New News."

Throughout his career, Ruddy has often staked out positions at variance with the Republican party. For Example, Ruddy broke with the Bush Administration on the Iraq War, and was one of the first conservatives to do so. "I came out very strongly against the war in Iraq when it wasn't in vogue, back in 2004," Ruddy told The Palm Beach Post. "I lost some subscribers. But we are close to spending a trillion dollars on the war and there is no exit strategy," he added. "Lots of Republicans and conservatives are not that gung-ho on the war anymore and I think we broke the ice."

In the fall of 2007, Ruddy published a positive interview with former President Clinton on Newsmax.com, followed by a positive cover story in Newsmax magazine. The New York Times noted with reference to the event that politics had made “strange bedfellows.”

A May 2009 New York Times Sunday magazine profile on the former President, "The Mellowing of william Jefferson Clinton," offered more details of the relationship between Ruddy and Clinton. The Arkansas Times said details about the friendship between Ruddy and Clinton in the New York Times profile was the "most amazing revelation" of their profile of the former President. Ruddy told the Times though he remained a "Reagan conservative", he had re-evaluated the Clinton presidency and suggested he had earned high marks as President for success in ending welfare, keeping government in check, and supporting free trade. Ruddy also noted that the Clinton Foundation was doing remarkable work globally.

During a 2010 campaign swing through Florida, President Clinton departed from his schedule to make a visit to Newsmax's offices in West Palm Beach. After a private meeting with Ruddy, Clinton toured Newsmax's offices and met with its staff.

A 2011 New York Times story on Newsmax detailed the company’s growing influence, especially Republican politics and noted that almost all of the party’s presidential candidates had made a "pilgrimage" to the company’s south Florida headquarters for a meeting with Ruddy.

In July 2012, Ruddy was a member of the official delegation that accompanied President Clinton on his five-nation tour of Africa, reviewing Clinton Foundation initiatives in the area of health care, HIV/AIDS programs, education, and poverty alleviation.

According to a 2014 profile in Bloomberg Businessweek, Newsmax generates over $100 million revenue annually. CNN reported that Newsmax was the third most-viewed political website in the nation, behind itself and Politico.

On June 12, 2017, Ruddy claimed that Trump met with Robert Mueller to offer him the job of FBI Director just days before it was announced that he would be appointed special counsel for the Russian investigation. Ruddy did not provide any proof of this. He also claimed in the same interview that Trump is considering terminating Mueller's position as special prosecutor. However, it was not clear if this was based on Trump's comments or the comments of his Lawyer made during the previous week.

Addressing the occurrence of noted tweets from President Trump on Friday night and Saturday in Politico, Ruddy said, “He understands the news cycle. ... It’s an opportunity to get out news on a Saturday, when other news organizations aren’t pushing too much new. He realizes that Saturday is a free media day for him.” The story described Ruddy as a Mar-a-Lago member and longtime friend of Trump’s.