Lerangis's work includes The Viper's Nest and The Sword Thief, two titles in the New York Times—bestselling children's-book series The 39 Clues, the historical novel Smiler's Bones, the YA dark comedy-adventure novel wtf, the Drama Club series, the Spy X series, the Watchers series, the Abracadabra series, and the Antarctica two-book adventure, as well ghostwriting for series such as the Three Investigators, the Hardy Boys Casefiles, Sweet Valley Twins, and more than forty books in the series The Baby-sitters Club and its various spin-offs. He has also written novels based on film screenplays, including The Sixth Sense, Sleepy Hollow, and Beauty and the Beast, and five video game novelizations in the Worlds of Power series created by Seth Godin. As a ghostwriter he has been published under the name A. L. Singer. He will be contributing the second entry in a four-novella collection, Vespers Rising, which will be published in April 2011 to serve as an introduction to a six-book 39 Clues sequel entitled Cahills Vs. Vespers. For this book series, he will write the third volume, to be published in March 2012.

Lerangis is the son of a retired New York Telephone Company employee and a retired public-elementary-school secretary, who raised him in Freeport, New York on Long Island. He graduated from Harvard University with a degree in biochemistry, while acting in musicals and singing with and musically directing the a cappella group the Harvard Krokodiloes, before moving to New York. He worked there as an actor and freelance copy editor for eight years before becoming an author.

In 2003, Lerangis was chosen by First Lady Laura Bush to accompany her to the first Russian Book Festival, hosted by Russian First Lady Lyudmila Putina in Moscow.Authors R. L. Stine (Goosebumps) and Marc Brown (the Arthur the Aardvark series) also made the trip with Bush.

Also in 2003, Lerangis was commissioned by the United Kingdom branch of Scholastic to write X-Isle, one of four books that would relaunch the Point Horror series there. A sequel, Return to X-Isle, was published in 2004.

In 2007, Scholastic announced the launch of a new historical mystery series called The 39 Clues, intended to become a franchise. Lerangis wrote the third book in the series, The Sword Thief, published in March 2009. On March 3, 2009, Scholastic announced that Lerangis would write the seventh book in the series, The Viper's Nest.

Lerangis lives in New York City with his wife, musician Tina deVaron, and their sons Nick and Joe.

Last Stop, the first book in Lerangis's science fiction/mystery series Watchers, was selected by the American Library Association as a 1999 Best Book for Reluctant Readers.

War, the fourth book in the series Watchers, was selected by the International Reading Association and the Children's Book Council as a 2000 Children's Choice book.

Lerangis's 2006 historical novel Smiler's Bones was a Junior Library Guild selection and was named among the New York Public Library Best Books for Teens 2006 and the Bank Street Best Books of 2006.Peter Lerangis has visited many schools. He is also a comedian.