A graduate of the University of California at Berkeley, Andersen joined the staff of Time Magazine as a contributing editor in 1969. From 1974 to 1986 Andersen was senior editor of Time Incorporated's People Magazine. He has also written for a wide range of publications, including The New York Times, The New York Daily News, Life, and Vanity Fair.
While his early nonfiction books veered from psychology (The Name Game) to true crime (The Serpent's Tooth) to art collecting (The Best of Everything, with former Sotheby's chairman John Marion), he is best known for his controversial biographies. Between 1991 and 2011, he published 14 New York Times bestselling biographies. The following year, Andersen's second book about the relationship of President John F. Kennedy and First Lady Jacqueline Kennedy, These Few Precious Days: The Final Year of Jack with Jackie, was published to coincide with the 50th anniversary of JFK's assassination and also became a Top 10 "New York Times" bestseller.
Seven of Andersen's titles have also been selected for the Readers Digest Today's Best Nonfiction Books of the Year series. In November 2008, NBC's Brian Williams presented Andersen with a Joan's Legacy Award for excellence in journalism regarding lung cancer, along with Ladies Home Journal, which excerpted the portion of his book Somewhere in Heaven: The Remarkable Love Story of Dana and Christopher Reeve describing Dana Reeve's battle with lung cancer. Madonna Unauthorized (1991) and The Day John Died (2000) were made into television films.
Andersen has promoted his books with appearances on TV programs such as the Today Show, Entertainment Tonight, Larry King Live, the CBS Early Show, Dateline, Extra, The O'Reilly Factor, NBC Evening News, Inside Edition, and Hardball.
Married since 1972 to former international banker Valerie Hess, Andersen resides in Connecticut. They have two daughters — former Bloomberg News White House correspondent Katharine Andersen Brower (born 1980) and artist Kelly Andersen (born 1990).
Andersen wrote Mick: The Wild Life and Mad Genius of Jagger to mark the 50th anniversary of the Rolling Stones in July 2012. The book quickly became Andersen's 15th New York Times bestseller. In a review in The Guardian, Dorian Lynskey noted: "A book about a singer that pays no attention to his songs is simply an anthology of gossip, albeit juicy, unusually well-researched gossip."
In Salon, Jake Tapper writes of Bill and Hillary: The Marriage: "Andersen dishes like a catty high school girl holding forth in the lunchroom, with little corroborating evidence for his claims, implied or otherwise." Entertainment weekly describes the book as "disenguous" and "[w]ritten to make big headlines and fast money, Bill and Hillary is a prime example of a kind of opportunistic celebrity muckraking – sometimes known as selling people out – that has become junky big business ....", noting Andersen "does that insidious, breezy thing of reconstructing extemporaneous conversations he couldn’t possibly have heard." According to People, "Andersen, clearly no fan of the First Couple, seizes on sleaze too much and with too little attribution. Titillating, perhaps, but in the end the book is merely banal,..."
- The Name Game (1977)
- Father (1983)
- The Serpent's Tooth (1986)
- Young Kate: Katharine Hepburn and the Making of an American Legend (1988)
- The Best of Everything (with John Marion) (1989)
- Citizen Jane (1990)
- Madonna: Unauthorized (1991)
- Jagger: Unauthorized (1993)
- Michael Jackson: Unauthorized" (1994)
- Jack and Jackie: Portrait of an American Marriage (1996)
- An Affair to Remember (1997)
- Jackie After Jack: Portrait of the Lady (1998)
- The Day Diana Died (1998, No.1 on the New York Times Best Seller List)
- The Marriage (Bill and Hillary) 1999
- The Day John Died (2000, about John F. Kennedy, Jr. Also reached No.1)
- Diana’s Boys: William and Harry and the Mother They Loved (2001)
- George and Laura: Portrait of an American Marriage (2002)
- Sweet Caroline: Last Child of Camelot (2003)
- American Evita: Hillary Clinton's Path to Power (2004)
- Barbra: The Way She Is (2006)
- After Diana: William, Harry, Charles, and the Royal House of Windsor (2007)
- Somewhere in Heaven: The Remarkable Love Story of Dana and Christopher Reeve (2008)
- Barack and Michelle: Portrait of an American Marriage (2009) 
- William and Kate: A Royal Love Story (2010)
- These Few Precious Days: The Final Year of Jack with Jacke (2013)
- Game of Crowns: Elizabeth, Camilla, Kate, and the Throne (2016)
- "Search Results for Christopher Andersen". Time. June 6, 2007.
- "Christopher Andersen". Daily News. New York.
- Weiner, Rachel (22 September 2009). "Obama complained, "Jesus I wish they'd stop grabbing..."". The Huffington Post.
- Lynskey, Dorian. "Mick: The Wild Life and Mad Genius of Jagger by Christopher Andersen – review", The Guardian, August 17, 2012
- Tapper, Jake. "The Clinton marriage", Salon, August 26, 1999
- "Bill and Hillary: The Marriage", Entertainment Weekly, August 20, 1999
- "Pics and Pans Review: 'Bill and Hillary: the Marriage'", People, Vol.52, No.8, August 30, 1999
- Christopher Andersen at the Internet Movie Database
- "Christopher Andersen", Bookreporter
- 'After Diana' Q&A With Christopher Andersen, CAROLINE HOWARD