Brandee Younger was born on July 1, 1983, and raised in Hempstead, New York, on Long Island. Her parents were music lovers rather than musicians, and she grew up on church choir singing, old-school R&B and hip-hop. Her first lessons were on piano with a family friend who was her church's organist. In school she played flute (she has said she picked it up by mistake, thinking it was a clarinet) and later trombone in band programs that she credits with her discipline. A woman who played harp as a hobby at her father's workplace pointed her toward the instrument, and she studied it privately while still in school. She earned undergraduate degrees in harp performance and music management at the Hartt School in West Hartford, Connecticut, and a Master of Music at New York University's Steinhardt School. A CD of Alice Coltrane's music that her father gave her showed her what the harp could do in a jazz band, and in college she studied standards and took informal lessons with jazz faculty. The tenor saxophonists Ravi Coltrane and Antoine Roney became her key mentors.

She made her public debut in 2007, at 23 and a graduate student at NYU, when Ravi Coltrane asked her to take part in the memorial service for his mother, Alice Coltrane, who had died that January. She has described the service as a turning point that set her three goals: building her own harp sound, playing inside a rhythm section, and writing her own music. Over the next decade she worked as a freelance harpist across jazz, hip-hop, R&B and pop. Her credits include Cassie's 2006 debut, Common's Finding Forever (2007), Ravi Coltrane's Blending Times (2009), Lakecia Benjamin's Retox (2012), Mack Wilds's New York: A Love Story and John Legend's Love in the Future (both 2013), Christian McBride's big band album Bringin' It (2017), and the 2017-18 sessions for Makaya McCraven's Universal Beings. She also worked with Pharoah Sanders, Jack DeJohnette, The Roots and Lauryn Hill.

Her own records began with the self-released EP Prelude (2011) and a live album by The Brandee Younger 4tet recorded at the Breeding Ground (2014), followed by Wax & Wane (2016), which includes her reading of Dorothy Ashby's "Afro Harping." Soul Awakening arrived on June 7, 2019, produced by bassist Dezron Douglas, with Ravi Coltrane guesting on two tracks, trumpeter Sean Jones and the singer Niia on one each, and covers of Ashby's "Games" and Alice Coltrane's "Blue Nile." In 2019 her composition "Hortense," in a version recorded for NPR Music in 2013, was heard in Beyoncé's Netflix concert film Homecoming, and she was chosen to perform her own music in the Soundtrack of America concert series created by Quincy Jones and Steve McQueen. Force Majeure, a duo album with Douglas recorded in their Harlem apartment between March and June 2020, during the pandemic lockdown, came out on International Anthem on December 4, 2020.

Her major-label debut, Somewhere Different, appeared on Impulse! on August 13, 2021. Douglas produced it, and it was recorded at Van Gelder Studio between November 2020 and February 2021 with drummer Allan Mednard, bassist Rashaan Carter and guests including Ron Carter and the singer Tarriona "Tank" Ball. Its track "Beautiful Is Black" earned a 2022 Grammy nomination for Best Instrumental Composition, which made her the first Black woman nominated in that category, and the album won a 2022 Edison Award for international jazz album. Brand New Life (Impulse!, April 7, 2023), produced by Makaya McCraven, is a tribute to Ashby that mixes Younger's originals, reworkings of Ashby's pieces and previously unrecorded Ashby compositions that Younger found while researching her life. Pete Rock, Meshell Ndegeocello, 9th Wonder and Mumu Fresh are guests. It won the 2024 NAACP Image Award for Outstanding Jazz Album, and she won the 2023 DownBeat Critics Poll in the Miscellaneous Instrument category for harp, after a Rising Star win in 2020. SFJAZZ named her one of its five Resident Artistic Directors for the 2023-24 season, and her residency there ran from March 6 to 10, 2024, with two nights built around Brand New Life and two honoring Alice Coltrane.

In 2024 the Coltrane family arranged for the harp that John Coltrane gave Alice in 1967, on which she recorded Journey in Satchidananda and A Monastic Trio, to be restored by the Chicago maker Lyon & Healy and lent to Younger. She recorded Gadabout Season on it at home. Released on Impulse! on June 13, 2025, it is an all-original set produced and engineered by Carter in a studio he built in the second bedroom of her Harlem apartment over several months in the second half of 2024, with Mednard on drums and guests Shabaka Hutchings (clarinet and flute), pianist Courtney Bryan, saxophonist Josh Johnson and Niia; Joel Ross and McCraven join on the title track. She received a 2025 Doris Duke Artist Award in jazz. As of April 2026 she teaches at New York University and The New School, and she appears on Terri Lyne Carrington's 2026 album Trip the Night Fantastic.

Younger treats the harp as a working member of a rhythm section as well as a lead voice, and her writing draws on the gospel, soul and hip-hop she grew up with as much as on jazz harmony. Her two stated models are Alice Coltrane, whose spiritual jazz she has covered and now plays on Coltrane's own instrument, and Dorothy Ashby, whose records of the 1950s and 1960s have been sampled across hip-hop and whom Younger cites for playing sophisticated lines while keeping the sound recognizably that of a harp. Her Impulse! albums have moved from the fusion-leaning band-and-guests approach of Somewhere Different and Brand New Life, where producers and rappers share the frame with jazz players, to a more restrained sound with electronic textures and extended harp techniques on Gadabout Season, a shift that HHV Mag noted in its review. She also teaches widely, with master classes and residencies at institutions that include Howard University, the University of Michigan, Berklee College of Music, Tulane University and Princeton University.