He was also a co-founder of Spy magazine, as well as co-creator and for its 20-year run host of the weekly Peabody Award-winning public radio program and podcast Studio 360.

"[7] Media critic Jack Shafer wrote in 2009 that Spy was one of "a handful of 20th-century American magazines...whose glory days continue to influence editors.

[10] In early 1996, according to a New York Times article quoting Andersen, Henry Kravis, the head of KKR, the financial firm that controlled New York's publishing company, asked him to kill a story about a rivalry between Felix Rohatyn and Steven Rattner for control of the Lazard investment bank, and to stop covering Wall Street altogether.

[14] From 2001 to 2004, Andersen served as a senior creative consultant to Barry Diller's Universal Television, where he co-created the entertainment and arts channel Trio with Michael Jackson, Lauren Zalaznick and Andy Cohen.

From 2003 to 2005 he was editorial director of Colors magazine, and in 2006, with his former colleague Jackson and Bonnie Siegler (and Diller's IAC) co-founded the daily email cultural curation service Very Short List.

In 2005 it won a Peabody Award for an hour-long documentary about Moby Dick, the first of its 17 American Icons hours, each exploring one cultural work––including The Autobiography of Malcolm X, 2001: A Space Odyssey, Monticello, and Disneyland and EPCOT.

The podcast, funded by the National Endowment for the Humanities and distributed by PRX/Public Radio Exchange, was drawn from hundreds of archival recordings unearthed from the Nixon and Lyndon Johnson presidencies.

His most recent novel, You Can't Spell America Without Me: The Really Tremendous Inside Story of My Fantastic First Year As President (Penguin, 2017) is a fictional memoir "by" Donald Trump co-authored by Andersen with Alec Baldwin.

He also wrote Reset (Random House, 2009), an essay about the causes and aftermath of the Great Recession, and he has contributed to many other books, such as Spark: How Creativity Works (HarperCollins, 2011), drawn from his interviews for Studio 360, an introduction to Heinrich Boll's novel The Lost Honour of Katharina Blum (Peinguin, 2010), and Fields of Vision: The Photographs of John Vachon (Library of Congress, 2010).

In 2017, he published Fantasyland: How America Went Haywire: A 500-Year History, which explains American society's peculiar susceptibility to falsehoods and illusions, and how that eventually led to Trump's election and the transformation of the Republican Party and the right in general.

The film director Steven Soderbergh initiated conversations with Andersen about Evil Geniuses when it was published, which led to the two of them co-creating Command Z, a satirical sci-fi series starring Michael Cera, Liev Schreiber and Roy Wood Jr. Soderbergh directed the eight episodes, which were released in July 2023 on his web site; all proceeds are going to charity.