In 1990, Duritz joined with Bryson in forming the band The Himalayans. In The Himalayans, Durtiz's songwriting talents were beginning to gain recognition from the other Musicians and the original version of the song "Round Here" was written at that time. A year later, while The Himalayans recorded a demo tape for a major record label, Duritz and Bryson independently submitted another demo tape of just the two of them singing stripped-down musical selections, and calling themselves Counting Crows. After both tapes were listened to, Duritz and Bryson's tape was selected, and they were asked to record the song for what would be their debut album. August and Everything After was the result, containing "Round Here". After they performed as the music guest on Saturday Night Live (SNL), their single "Mr. Jones" jumped 40 spots in the charts.

Duritz has collaborated with The Wallflowers (led by Jakob Dylan) on the album Bringing Down the Horse on the track "6th Avenue Heartache"; with Ryan Adams on Gold and the song "Butterfly in Reverse" from Hard Candy; with Peter Stuart on Propeller and Daisy; with Live on V; and with Dashboard Confessional on the track "So Long, So Long" from Dusk and Summer. He also collaborated with Nanci Griffith on "Going Back to Georgia" and "Talk To Me While I'm Listening" from Griffith's 1994 Album Flyer.

In 1995, Duritz dated Jennifer Aniston. He has also dated Courteney Cox, Monica Potter, Samantha Mathis, and Winona Ryder.

In 1997, Adam Duritz co-founded E Pluribus Unum, an independent label in which he retained ownership. Before the label was purchased by Interscope Records in 2000, Duritz had signed Joe 90, Gigolo Aunts, and Neilson Hubbard—all of whom he had taken on the road to open for Counting Crows.

In addition to his musical pursuits, Duritz was executive Producer for the film The Locusts. He appeared in the 2007 mockumentary film Farce of the Penguins. Adam teamed with the Broken Lizard comedy troupe in 2009 as Executive Producer for the film Freeloaders (2011). The film revolves around "five guys and a girl who live in the lap of luxury in a rock star's mansion. But their sweet situation is threatened when the rock star decides to sell the home. The friends will do whatever it takes to maintain their rock and roll lifestyle, as hilarity and shenanigans ensue." Written by Dan Rosen and Dave Gibbs, the film stars Clifton Collins Jr., Olivia Munn, Jane Seymour and Dave Foley as well as a multitude of stars making brief cameos throughout.

In 2008, Duritz revealed he has grappled with a dissociative mental-health issue.

In October 2009, Duritz was reported to be dating Shameless Actress Emmy Rossum, with whom he had toured during the summer of 2009. Rossum and Duritz broke up in September 2010. Duritz was reported to be unmarried as of August 2014.

Duritz was also a judge for the 10th annual Independent Music Awards to support independent artists' careers.