Seamus Blake was born in London on December 8, 1970 and raised in Vancouver, British Columbia, where his mother introduced him to jazz as a child. He went east to the Berklee College of Music in Boston, and the association that has run longest in his career began while he was still a student there: at twenty-one he was asked to record with Victor Lewis, and his first commercially issued credit is the tenor chair on Lewis's Know It Today, Know It Tomorrow (Red Record, 1993), on which he also contributed a composition. A second student-era date, Franco Ambrosetti's Live at the Blue Note (Enja, 1993), followed in the same year.

He moved to New York after graduating and was recording as a leader within months. The Call was cut at RPM Studio on December 24, 1993 and issued by the Dutch label Criss Cross Jazz in 1994, with a band that reads now like a roll call of his generation: Kurt Rosenwinkel on guitar, Kevin Hays on piano, Larry Grenadier on bass and Bill Stewart on drums. Seven of the nine pieces are Blake's own. Criss Cross became his label for the next two decades, and the sideman work arrived at the same rate: Billy Drummond's The Gift (1994), Hays's Seventh Sense (Blue Note, 1994) and Go Round (Blue Note, 1995), Darrell Grant's The New Bop (1995), a guest spot on Mark Turner's Yam Yam (1995), and Bill Stewart's Telepathy (Blue Note, 1997). He also joined the Mingus Big Band, and stayed: he plays on six of the Charles Mingus repertory bands' records between 1996 and 2006, four of which drew Grammy nominations for Best Large Jazz Ensemble Album.

His own catalogue refused to settle into one idiom from the start. The Bloomdaddies (Criss Cross, 1996), recorded in New York on December 16, 1995, is a two-tenor electric band with Chris Cheek, Jesse Murphy on bass guitar and drums split between Dan Rieser and Jorge Rossy; the group later made a second album, Mosh for Lovers, for Fresh Sound New Talent in 2002. Four Track Mind went back to acoustic post-bop with Turner and Tim Hagans added to the front line, and Stranger Things Have Happened (Fresh Sound New Talent, 1999) put Rosenwinkel, Grenadier and Rossy in a pianoless quartet. Sun Sol (2000) was co-led with the Catalan drummer Marc Miralta, with Avishai Cohen on double bass. Echonomics, recorded at Systems Two in Brooklyn on December 15, 1999 and released in February 2001, brought in David Kikoski, Ed Howard and Victor Lewis, and began the working relationship with Kikoski that has now lasted a quarter of a century.

In February 2002 Blake took first place in the Thelonious Monk International Saxophone Competition in Washington, D.C., collecting a $20,000 prize and playing with Wayne Shorter and Herbie Hancock as the winner. The decade that followed was his most settled as a bandleader. A quintet with Kikoski, Lage Lund on guitar, Matt Clohesy on bass and Bill Stewart on drums made Way Out Willy (2007, recorded March 19, 2006), Bellwether (2009, recorded December 11, 2008) and the live Live at Smalls (2010, taped at the Greenwich Village club on August 31 and September 1, 2009). Alongside it he was the tenor voice in the Criss Cross co-operative Opus 5 with Alex Sipiagin, Kikoski, Boris Kozlov and Donald Edwards, from Introducing Opus 5 (2011) through four more albums to Swing on This (2022), and in BANN, the co-operative quartet with Oz Noy, Jay Anderson and Adam Nussbaum whose one album As You Like appeared on the Italian label Jazz Eyes on October 25, 2010. He also made two records with Sam Yahel and Ari Hoenig and one with the Bloomdaddies rhythm section's successors, and took a two-tenor project called Reeds Ramble back into the studio with Cheek, Ethan Iverson, Matt Penman and Jochen Ruckert for Reeds Ramble (2014) and Let's Call the Whole Thing Off (2016).

Superconductor (5Passion, December 2015) is the record where the two halves of his playing life met. It is the first album on which he uses the EWI, the electronic wind instrument, and it sets Scott Kinsey's keyboards, Matthew Garrison's electric bass and Nate Smith's drums against three tracks scored for a small orchestral ensemble by Guillermo Klein, with John Scofield guesting on three pieces and Gonzalo Rubalcaba on one. It was nominated for a Juno Award for Jazz Album of the Year. The same period put him in Antonio Sanchez's Migration band for The Meridian Suite (2015), where he doubles tenor and EWI, and on Rubalcaba's Suite Caminos (2015), which was nominated for the Grammy for Best Latin Jazz Album.

Europe took over from New York in stages. In 2017 he assembled a quartet in Paris, the French Connection, with Tony Tixier on piano, Florent Nisse on bass and Gautier Garrigue on drums; they recorded Guardians of the Heart Machine at Studio de Meudon on November 11 and 12, 2017, and Whirlwind Recordings issued it in 2019 as his first release on vinyl. He has since lived in Amsterdam, Rome, Porto and Paris, and his current base is Cologne. He teaches as a guest at Dutch conservatoires, including the Conservatorium van Amsterdam's Keep an Eye Summer Jazz Workshop. In 2022 he joined Roger Waters's road band for the This Is Not a Drill tour, playing saxophone on Pink Floyd repertoire in stadiums for the next three years, and he is credited on the resulting concert album This Is Not a Drill (Live from Prague) (Columbia and Legacy, 2025).

The recent leader catalogue is unusually varied even by his standards. New York Factor Vol. 1 (August 2022) is a straight tenor-quartet date with Kikoski, Alexander Claffy and both Bill Stewart and Victor Lewis on drums, cut at Big Orange Sheep on September 21 and 22, 2021. moosejaww, three months later, is not a jazz record at all: Blake plays guitar and sings on it, in a band with Kris Bauman, Al Street and Ruckert. From Angels (June 2024) is a saxophone and piano duo with the Italian pianist Alessandro Lanzoni, taped at Cicaleto studios in December 2022. Caipora, co-billed with the Brazilian drummer Edu Ribeiro, appeared on Blaxtream in September 2025, and The Electrifying Seamus Blake Plays the Music of Eddie Harris: EH!, recorded at Afterlife Studios in Vancouver on November 3 and 4, 2025 with Sam Yahel on Hammond organ, Tim Lefebvre on electric bass and Corey Fonville on drums, was his first release for Cellar Music Group in July 2026.

Blake's tenor sound is broad, dark and centred, and the thing that identifies him fastest is not tone but line length: long, evenly articulated eighth-note phrases that keep their shape through several choruses and resolve chromatically rather than on the obvious note. He came up alongside Mark Turner and Chris Cheek in the New York tenor generation that took Joe Henderson and Warne Marsh as models rather than John Coltrane alone, and the two-tenor records he has made with Cheek, from The Bloomdaddies in 1996 to Let's Call the Whole Thing Off twenty years later, are the clearest documents of what that generation actually sounds like when two of its members play the same tune. John Scofield, who hired him for the touring version of his Quiet band, called him "extraordinary, a total saxophonist," and the phrase catches the range: the same player who cut an acoustic Criss Cross quintet date every couple of years also fronted an electric band, took up the EWI on Superconductor in 2015, sings and plays guitar on his own indie-rock record, and spent three years as the improvising soloist in a stadium show built on Pink Floyd. His writing runs to long-form heads with displaced phrase lengths and to reharmonised standards, and he has made a habit of pulling material from outside jazz entirely: a movement of a Debussy string quartet became a set piece for his quintet, and As You Like opens with "All the Things You Are" and closes with Joe Henderson's "Isotope" by way of a Crosby, Stills and Nash song.