Dario Deidda was born on March 1, 1968, in Salerno, into a family that treated music as a given rather than a hobby: his parents were both pianists, and his brothers Alfonso and Sandro also became professional musicians. He started on drums at six, moved to bass soon after, and at thirteen enrolled in the classical double bass program at Salerno's own conservatory, the Conservatorio "Giuseppe Martucci" - the same institution where he has taught jazz electric bass since 2004.

His earliest credits ran through Salerno's own scene: guitarist Piero Condorelli's Sonora Art Quartet, a family group billed as the Deidda Brothers, the Salerno Liberty City Band, and the Cuban-tinged Cuban Stories project with his brother Alfonso and percussionist Ernesttico Rodriguez. His first outing as a billed leader, 3 From the Ghetto (2003, Go Jazz), paired him with pianist Julian Oliver Mazzariello and drummer Stephane Huchard under producer GeGè Telesforo; Groove Master Edition reissued it in 2006.

From the late 1990s on, his Discogs credit sheet reads like a directory of Rome's working post-bop scene. He is on drummer Roberto Gatto's 7# (1997) alongside Argentine saxophonist Javier Girotto, then on two further Gatto leader dates; on alto saxophonist Rosario Giuliani's Live From Virginia Ranch (1998), a quartet date featuring pianist Franco D'Andrea with drummer Massimo Manzi; on tenor saxophonist Emanuele Cisi's 2001 Sonny Rollins tribute; and on American tenor player Larry Schneider and Gaspare Di Lieto's Lemon Lips (2000). He is the bassist on alto saxophonist Carla Marciano's 2002 debut Trane's Groove, and later worked repeatedly with guitarist Guido Di Leone - including a 2020 tribute-to-Jim-Hall session alongside the American guitarist Peter Bernstein - and with Nicola Conte on Rituals (2008). In 2012 he is the bassist on Enrico Rava and the Parco della Musica Jazz Lab's ECM album Rava on the Dance Floor.

Running alongside that jazz career is a substantial, separately documented career in Italian popular music: Deidda toured with American singer Carl Anderson (playing Judas in stage productions of Jesus Christ Superstar) from 1998 to 2003, with singer-songwriter Pino Daniele in 1999, and was pop vocalist Fiorella Mannoia's touring and recording bassist from 2003 to 2007, appearing on four of her studio and live albums plus two live-video releases. That work is real, well documented, and not hidden here - but it runs alongside, not instead of, a continuous and still-active jazz career: Musica Jazz's Jazzit Award named him Italy's best jazz bassist in eight separate years (some later press rounds the figure up to ten; the eight-time figure is the one repeated most consistently across independent sources and is used here), and as of this profile he continues to release both as a leader - 11 Little Things (2019, with pianist Roberto Tarenzi and drummer Roberto Pistolesi), In Duo: Live at Duke Jazz Club (2023, a duo record with Guido Di Leone), and the big-band session Brassing (2026, credited to Rosario Giuliani featuring Deidda, pianist Pietro Lussu, and drummer Sasha Mashin, with trumpeters Fabrizio Bosso and Claudio Corvini) - and as a first-call sideman.

His most visible jazz credential internationally is a standing membership in guitarist Kurt Rosenwinkel's stripped-down trio, captured on the 2020 studio album Angels Around (Heartcore Records) with drummer Gregory Hutchinson, and documented live with drummer Eric Harland at Oslo Jazzfestival in August 2017 - a performance reviewed by the American jazz press (All About Jazz covered Angels Around on its release), which is a rare notice for an Italian sideman's work to receive. He has also self-released a solo bass record, My Favorite Strings, Vol. 1 (2018, Groove Master Edition, with GeGè Telesforo), reported by his own promotional material to have reached the top of the iTunes jazz chart - reported as stated, not independently verified for this profile.

Deidda calls his own approach "low jazz" - the title of his instructional book, My Way: The Low Jazz, From Technique to Creativity - and works comfortably across fretted and fretless electric bass, double bass, and (on the Tricycles project) electric cello. His session work spans a tight stylistic range within jazz: the harmonically dense post-bop rhythm-section role he plays for Gatto, Giuliani, and D'Andrea; the chamber-funk/fusion textures of Tricycles' Eclectricity (2012); and the spare, unhurried time-feel that Kurt Rosenwinkel's trio format asks for, where there is no piano to fill space and the bass line carries much of the harmony. That range, more than any single influence, is what session leaders across three decades of Italian jazz have kept calling him back for.