Julian Price Lage was born on December 25, 1987, in Santa Rosa, California, the youngest of five children. He picked up the guitar at five. By the time he was eight he was the subject of a short documentary, Jules at Eight (1996), and had played with Carlos Santana. At 12 he performed at the 2000 Grammy Awards, a broadcast that led Gary Burton to seek him out. Lage studied classical music at the San Francisco Conservatory of Music, took courses at Sonoma State University and the Ali Akbar College of Music, and at 15 joined the faculty of the Stanford Jazz Workshop.

Burton became his mentor. At 13 Lage played "A Night in Tunisia" with Burton and Herbie Hancock, and as a teenager he toured with Burton's quintet and recorded Generations (Concord Jazz, 2004) and Next Generation (2005) with him. Burton also steered him to the Berklee College of Music, where he graduated in 2008. Burton's New Gary Burton Quartet, with Lage, bassist Scott Colley and drummer Antonio Sanchez, made Common Ground (Mack Avenue, 2011) and Guided Tour (2013) before Burton retired from performing in 2017.

Lage's own debut, Sounding Point (EmArcy, March 24, 2009), brought guests including banjoist Béla Fleck and mandolinist Chris Thile and was nominated for a 2010 Grammy Award for Best Contemporary Jazz Album. Gladwell followed in 2011. He then built a run of duo records with other guitarists and pianists: Free Flying (Palmetto, 2013) with Fred Hersch, taken from live sets at Jazz at Kitano in New York; Avalon (2014) and Mount Royal (Free Dirt, 2017) with Chris Eldridge, the second a Grammy nominee for Best Contemporary Instrumental Album; and Room (Mack Avenue, 2014) with Nels Cline. Around the time of the 2015 solo acoustic album World's Fair he struggled with focal dystonia, which caused spasms in his left hand, and he has said he had to relearn how he held and played the guitar. Arclight (Mack Avenue, 2016) used a trio with Scott Colley and Kenny Wollesen, and Modern Lore (2018) a similar lineup with keyboardist Tyler Chester added; it was nominated for a Grammy in the Best Contemporary Instrumental Album category.

In 2019 Lage made Love Hurts (Mack Avenue), mostly covers recorded live in the studio at The Loft, Wilco's rehearsal and recording space, with bassist Jorge Roeder and drummer Dave King; his solo on Ornette Coleman's "Tomorrow Is the Question" was nominated for a Grammy for Best Improvised Jazz Solo. The Blue Note signing was announced on March 17, 2021, and the same Roeder and King trio made Squint (June 11, 2021). View with a Room (September 16, 2022) added the guitarist Bill Frisell, and the companion EP The Layers (March 17, 2023) drew a Grammy nomination for Best Contemporary Instrumental Album. Speak to Me (March 1, 2024), produced by Joe Henry and widening the band with Kris Davis, keyboardist Patrick Warren and reed player Levon Henry, was also nominated, at the 2025 Grammys. Scenes from Above (January 23, 2026), again produced by Henry, introduced a quartet with John Medeski on piano and organ, Roeder on bass and Wollesen on drums.

Outside his own bands he has been a regular guitarist for John Zorn, appearing on more than twenty Tzadik albums since 2017, and has played guitar for the saxophonist Charles Lloyd, on 8: Kindred Spirits (Blue Note, 2020) and Trios: Sacred Thread (2022). He is a member of the quartet on Paramount Quartet (ECM, released May 29, 2026), led by Joe Lovano, with bassist Santi Debriano and drummer Will Calhoun. He teaches ensembles and guitar at The New School's School of Jazz and Contemporary Music, which announced his faculty appointment in September 2019, and is based in New York City. In June 2026 he began playing guitar with Bob Dylan's touring band on an intermittent basis, first replacing Doug Lancio at the Santa Barbara Bowl on June 17 and returning for stretches of the summer tour; a July report said he would instead be on the road with his own quartet during Dylan's fall European dates.

Lage plays with a clean, unforced tone and a melodic, song-shaped approach to improvising, and his own tunes are usually short and tightly built. His reference points reach well past jazz: he has named Bruce Springsteen, Bo Diddley and Little Richard among his earliest heroes, credits Gary Burton, John Zorn and Jim Hall as mentors, and began concentrating on a Fender Telecaster around 2016, after which his music grew more spare and more country-tinged. His repertoire shows the same range: Love Hurts covers Ornette Coleman ("Tomorrow Is the Question"), Keith Jarrett ("The Windup" and "Encore (A)"), Jimmy Giuffre ("Trudgin'"), the Everly Brothers hit that gives the album its title and the Peter Ivers and David Lynch song "In Heaven", and Mount Royal places him beside a bluegrass guitarist in a program that moves between acoustic jazz and bluegrass instrumentals. Squint was praised by DownBeat as a modern take on the Blue Note tradition, and Speak to Me holds a Metacritic score of 91 from four reviews. AllMusic files him under Guitar Jazz and Modern Jazz. For Scenes from Above he has said he wrote the pieces in short sprints of about twenty minutes each, hoping to give the new quartet something to talk about once they were together.