Andrev Walden grew up in Norrköping. He studied journalism at Bona Folkhögskola but never completed his studies. Later, he got a job at Aftonbladet as an editor and eventually became the editor-in-chief of the fiction department. After 13 years at the newspaper, he resigned and then worked as an editor and program director for the SVT television series Sociala Monster and as an editor for Filip & Fredrik’s show Breaking News. In 2016, Walden returned to Aftonbladet as a columnist and wrote for them until the end of 2018, when he joined Dagens Nyheter. He also frequently writes for Café.

In 2017, Andrev Walden was nominated for the Stora Journalistpriset (the Grand Journalism Award) in the "Voice of the Year" category. The jury's motivation stated: "Because he finds everyday drama in big issues, makes us laugh, and helps us see the world, family, and ourselves in a new, slightly wiser light."

Walden illustrated his own book, and his writings mainly focus on topics such as children, space, and apocalypse.

In 2023, Walden made his literary debut with the novel Jävla karlar, published by Bokförlaget Polaris. The book is based on his own experiences growing up. It received positive critical reception, and on November 27, 2023, it was awarded the August Prize in the fiction category.