Mehdi Chaib began saxophone at a conservatory at the age of 8 and came to jazz and improvisation at 17. In 2000 he moved to Paris to study at the American School of Modern Music, and rather than settling into the conservatory-to-club track he attached himself to two working collectives at once: Tarace Boulba, the funk fanfare founded in Montreuil in 1993 by two former members of Les Négresses Vertes, and Zetlab. Both were large, open, self-organized ensembles, and the habit of playing inside a big collective rather than a quartet has shaped everything he has done since.

Between 2003 and 2008 he toured Mali, Senegal, Morocco, and the Comoros. His own biographies name that stretch, rather than any conservatory year, as the turning point in how he plays. The first recorded evidence of what came out of it is Zetlab's Urban Ethnic Jazz (Suglab Records, 2006), where Chaib is not just the tenor saxophonist but a co-producer and the composer of two of the album's tracks. The band on that record matters for what followed: the oud player was Thierry Fournel, and the singer and guimbri player, credited as Jawed El Garouj, was Jaouad El Garouge. Both would become his partners three years later. Benjamin Moussay played piano and Rhodes, Stéphane Edouard played drums and percussion, and Da Brains supplied the raps, which puts the album at the exact crossing of jazz, Maghrebi ritual music, and hip-hop where Chaib has worked ever since. He turned up on the other side of that crossing the following year, playing tenor and soprano saxophone on "Qidar" for the French beatmaking trio Jazz Liberatorz on Clin d'Oeil (Kif Recordings kifhh120, 2007), a track he is also credited with co-writing.

Two long-running ensembles date from the end of that decade. In 2008 he became one of three co-directors of the 93 Super Raï Band, a twenty-piece orchestra run under the Villes des Musiques du Monde banner in Seine-Saint-Denis, sharing direction with the trumpeter Patrick Touvet and the percussionist Samir Inal and playing soprano saxophone in it. In 2009 he founded Global Gnawa with Fournel and El Garouge, the two Zetlab colleagues, building a group around the Moroccan gnawa repertoire that El Garouge carried and the free-jazz saxophone that Chaib brought to it, with afrobeat, reggae, and ethio-jazz pulling at the edges. He plays soprano and tenor saxophone, karkabou, bendir, and sings in the group, which later expanded to a quartet with the percussionist Adhil Mirghani and recorded "Zemedi" in 2010 for Tour'n'sol Prod.

The association that made his name in jazz proper began in 2011, when the Franco-Syrian flutist Naïssam Jalal formed Rhythms of Resistance and gave Chaib the saxophone chair. He has held it ever since, playing tenor, soprano, and sopranino alongside percussion, next to Karsten Hochapfel on guitar and cello and a rotating rhythm section. Between the founding of that band and its first record he made the trip to a session that put him on an American jazz release: he was in Studio Sequenza in Montreuil, the town where Tarace Boulba had been based since 1993, on July 2 and 3, 2013, for Omer Avital's New Song. Avital had come to France to cut the album with Avishai Cohen on trumpet, Joel Frahm on tenor, Yonathan Avishai on piano, and Daniel Freedman on drums. Chaib was the local musician brought in for the North African material: he sings the lead vocal on "Tsafdina," plays karkabas on "Maroc," and joins the whole band in the choir on "Tsafdina" and "Small Time Shit." The record was licensed to Motéma Music and issued in the United States as MTA-CD-161.

Rhythms of Resistance then produced the run of albums that carried Chaib's playing furthest. Osloob Hayati (Les Couleurs Du Son NJ001), recorded in April 2014 and released on March 30, 2015, has him on tenor and soprano saxophone plus derbuka and karkabu, with Mátyás Szandai on bass and Francesco Pastacaldi on drums. Almot Wala Almazala, recorded in May 2016 and released that November, was the breakthrough: it took the Académie Charles Cros Coup de Coeur in 2017, four "f" from Télérama and four stars from Jazz Mag, and became the fourth best-selling jazz album in France in the year of its release, at more than four thousand copies. Arnaud Dolmen joined on drums for it. Chaib was working the hip-hop side of the same circle in parallel, playing tenor and soprano saxophone and percussion in Al Akhareen, the sextet built around the Palestinian rapper Osloob and Jalal, whose self-titled album came out on Les Couleurs Du Son in 2018 with Viryane Say on bass, Clément Cliquet on drums, and DJ Junkaz Lou on turntables. The same year he played soprano and alto saxophone, karkabas, and backing vocals on Fanfaraï Big Band's Raï Is Not Dead (Tour'n'sol Prod. FAN003), a raï big band of fifteen credited players featuring the Oran guitarist Lotfi Attar and the singer Sofiane Saidi.

He has kept both halves of the work going since. Rhythms of Resistance's third album, Un Autre Monde (Les Couleurs Du Son CDS 238930, released March 5, 2021), pairs a quintet studio session recorded in June 2020 at Midi Live in Villetaneuse with live material taped in Brittany in February 2020, and adds the Orchestre National de Bretagne under Zahia Ziouani; Chaib plays tenor and sopranino saxophone and karkab on it. In 2024 he appeared on Bab L' Bluz's Swaken for Real World Records (CDRW259, May 10, 2024), credited not on saxophone at all but on ney, kawala, and zorna, and he played the Gnaoua and World Music Festival in Essaouira. He was still in the Rhythms of Resistance line-up for the 2024-25 season, alongside Jalal, Gabriel Gosse, Damien Varaillon, and Arnaud Dolmen, and he continues to direct an orchestra of amateur musicians in Seine-Saint-Denis.

Chaib is a saxophonist whose whole identity rests on refusing to be only a saxophonist. The free-jazz energy he brings to Global Gnawa is what the group's own promotional material leads with, and Télérama described that band's sound as very free and galvanizing, but on the same stage he will put the horn down and pick up the karkabas, the iron castanets that drive gnawa ritual music, or the derbuka. The doubling is not decorative: on nearly every record he has made, the credit reads saxophone and percussion together, and on Avital's New Song the karkabas and the lead vocal, not the saxophone, are what he was hired for. That makes him a rare kind of specialist in the Paris scene, a conservatory-trained improviser who can carry the ritual instruments and the vocal tradition of gnawa with enough authority to be credited on a Real World album for ney, kawala, and zorna and none of the saxophones. His playing in Rhythms of Resistance sits inside Naïssam Jalal's compositions rather than on top of them, tracking her flute and ney lines in unison or in close harmony and then breaking out; critics writing about Almot Wala Almazala and Un Autre Monde have described the group as retying the links between jazz, Western classical music, and classical Arabic music, and Chaib is the member whose instrument case makes that description literal. The influences he acknowledges are geographic rather than personal: the 2003 to 2008 tours through Mali, Senegal, Morocco, and the Comoros are what he names as the source of his expression, and the Maghrebi and gnawa repertoires are what he keeps returning to across five separate ensembles.