Kepnes was born in Boston. At 23, he had never left the United States. In 2005, however, he took a trip to Thailand. The trip convinced Kepnes to quit his job, finish his MBA, and begin traveling the world and blogging about his experiences. Kepnes has since traveled to more than 70 countries in his 7 years of traveling.

In 2008, Kepnes started NomadicMatt.com to record his stories and monetize his traveling. He also runs an online blogging school called Superstar Blogging where he offers online courses in blogging and also hosts other courses, including a course on photography run by travel photographer Laurence Norah.

Kepnes’ first book, How to Travel the World on $50 a Day: Travel Cheaper, Longer, Smarter, was published in 2013 by Penguin. Writers from the New York Times, National Geographic, and Outside Television blurbed the book. Matt Gross of the New York Times said, “Whether you’re a savvy backpacker or just dreaming of getting a passport and going overseas, Matt’s collection of easy-to-employ money-saving strategies will open your eyes to the near-infinite ways of seeing the world without busting your budget.” The book outlines Kepnes’ belief that travel can be inexpensive while still being extensive. It offers tips for getting free sky miles, avoiding overseas bank fees, and finding cheap accommodations. The book was a New York Times bestseller.

In July 2019, Kepnes published his memoir, Ten Years a Nomad: A Traveler’s Journey Home.