Neiwert was raised in Idaho Falls, Idaho, and attended the University of Idaho, where he obtained his B.A. in English (1984), as well as the University of Montana (1987–88), where he studied creative writing. He worked at newspapers around the Pacific Northwest from 1978–1996, notably in Idaho (at Sandpoint, Blackfoot, Lewiston, Moscow, and Twin Falls); Missoula, Montana; and western Washington (Kent, Bellevue, and Seattle). He went to work at MSNBC.com in 1996 as a writer-producer, and continued there through late 2000. Since then, he has focused on writing books and producing his blog Orcinus, which tends to report on the crossover between the mainstream and the far right. The blog won early recognition in the liberal blogosphere in the form of consecutive Koufax Awards for Best Series in 2003 and 2004. The Northwest Progressive Institute named its annual awards to the region's best liberal bloggers after Neiwert. He edited the political blog Crooks And Liars from 2008-2012. He is currently a contributing writer for the Southern Poverty Law Center's blog, Hatewatch. His book And Hell Followed With Her: Crossing the Dark Side of the American Border, won the 2014 International Latino Book Award for general nonfiction.
He has been married since 1989 to Lisa Dowling of Helena, Montana. They live together in Seattle with their daughter, Fiona, born in 2001.