Gino Marinacci was born on August 24, 1926 in Raiano, in Italy's Abruzzo, and grew up in Cittaducale, near Rieti. His father, Umberto, led the town band, and local biographies say the boy first played in it on a small clarinet at six or seven. He trained in Rome at the Collegio di Musica della Gioventù Italiana, the section of the Santa Cecilia Conservatory, specializing in clarinet and then the whole saxophone family, soprano through baritone.

He made his living as an orchestra player. The Conca Peligna biography of him says he sat on baritone saxophone and bass clarinet in the symphonic and rhythm-symphonic orchestras of RAI and in the RCA Italiana orchestras that recorded under Ennio Morricone, Bruno Maderna, Franco Ferrara and Riccardo Muti, and that he belonged to the rhythm-symphonic orchestra of Radio Turin under Armando Trovajoli. Discogs supports the Trovajoli link: it credits him on flute on Trovajoli's Softly (1959) and on baritone saxophone on Ragazza Mia (1960) and The Beat Generation (1960). The same biography names Mario Gronchi, the son of a former President of the Italian Republic, among his best saxophone pupils.

The jazz side of that career is documented from 1957. He plays baritone saxophone on two Nunzio Rotondo pieces, "Thaganoghi" and "Noghitonghi Thagani," on Romano Mussolini's RCA Italiana LP with Rotondo and Lilian Terry, recorded between June and November 1957 with Romano Mussolini on piano. In January 1958 he is the baritone saxophonist on "The Men Blowin'" at the Sanremo Jazz Festival, in a band with Gil Cuppini on drums, and in 1959 he plays flute and baritone saxophone on Rotondo's LP The Artistry Of Nunzio Rotondo with Cuppini again at the drums. On Trovajoli's The Beat Generation (RCA, 1960), a big-band set of West Coast-style charts by Bill Russo, Bill Holman and William O. Smith, he is the baritone saxophonist in a section that also lists Gianni Basso, Attilio Donadio, Dino Piana and Baldo Panfili; Musica Jazz's 1989 cover-mount LP Italian Jazz Graffiti 2 carries a "Blues" (Bill Russo) credited to the same lineup.

Piero Umiliani put him in the Rome film-score sessions that also brought in Chet Baker. Marinacci is the baritone saxophonist on five tracks of Baker's Italian Movies (Liuto, 1990), which Discogs ties to the film Big Deal On Madonna Street, and on "Lyda," dated Rome, 1959, on the Musica Jazz compilation Jazz & Noir, where Baker is credited on trumpet. He is also credited on "Arrivederci" in the 2014 box Chet Baker Sings: The Complete 1953-62 Vocal Studio Recordings, and on two 1960s film-score records with a jazz cast: 3 Notti D'Amore (CAM, 1964), where Gato Barbieri is credited on tenor saxophone on the same tracks, and Umiliani's La Legge Dei Gangsters (Omicron, 1969, recorded in Rome in November 1968), with Cicci Santucci on trumpet.

His records under his own name start in 1960 with Amorevole, a four-track RCA Italiana EP billed to the Gino Marinacci Ensemble: flute on the A side, in Morricone arrangements, and baritone saxophone on the B side with a five-trumpet section that includes Baldo Panfili. In 1963 CAM co-billed him with the composer and arranger Gianni Ferrio on the bossa nova album Lady Bossa Nova In Italy, with the singer Marina Moran. In 1964 and 1965 he led a group with the vibraphonist Carlo Zoffoli and the harpist Anna Palomba, on the EP More (Ti Guarderò Nel Cuore) and the LP Arpa In Jazz, recorded on January 20, 1965 at Dirmaphon Studios: harp-led settings of themes by Piero Piccioni, Trovajoli, Nino Rota, Morricone and others.

In 1966 a car accident on the Aosta-Ivrea motorway left him in a wheelchair for the rest of his life. Local biographies from Cittaducale and Rieti say he went on to study at Berklee College of Music in Boston. The years after the accident are the best documented of his career as a leader. Il Flauto Di "Gino Marinacci" (Leonardi Records, 1970) is a twelve-track set of short instrumental themes composed by Ferrio, Domenico Dell'Aera and Plakoti. .....Idea (RCA Original Cast, 1971) puts him on flute, alto flute and bass flute in a sextet with Dino Piana on trombone, Antonello Vannucchi on piano and organ, Angelo Baroncini on electric guitar, Maurizio Majorana on bass and Roberto Podio on drums; Marinacci arranged eight of its eleven tracks, and the closer is Piccioni's "Un Volto Una Storia," which Piccioni had also issued as a 1969 single with Marinacci on bass flute. In 1971 he won the international Armstrong prize at Venice's Mostra Internazionale di Musica Leggera, awarded to the best Italian jazz musician.

In 1972 RAI's Programma Nazionale broadcast Amico Flauto, four Thursday-night episodes at 22:10 from the Teatro delle Vittorie in Rome, between May 18 and June 8, hosted by Renzo Arbore and built on Marinacci's musical ideas. According to Italian Wikipedia's entry on the series, Marinacci played flute, bass flute and baritone saxophone, led an ensemble called I Flauti di Gino Marinacci and played with the Orchestra dei Solisti della RAI in arrangements by Franco Goldani; the guests it lists include Mina, Trovajoli, Piccioni and the trumpeter Art Farmer. The companion LP on the Idea label (IL 5001) credits Dino Piana on trombone, Severino Gazzelloni on flute on one track and Trovajoli on spinet.

The same year Roman Record Company issued Atom Flower's (RCP 711), recorded at Piero Umiliani's Sound Work Shop studio: eight tracks by Franco Goldani and Frank Pidgeon, with Giovanni Tommaso on electric bass, Dino Piana on trombone, Alfio Galigani, Quarto Maltoni, Livio Cerveglieri and Sal Genovese doubling on flute, Vannucchi on keyboards and a string quartet. Discogs tags it Jazz-Funk, Modal and Smooth Jazz. Mono Jazz reissued it on LP in 2021 and on CD in 2023, with a remastered digital edition the same year, prepared from the original tapes under the supervision of the Marinacci family. An LP simply titled Gino Marinacci followed on Idea in 1976, ten tracks by Edmondo Rossi and Dell'Aera including "Barocco 73" and "Bach Round Time."

Marinacci died in 1982. A Gino Marinacci Association was founded in Cittaducale in 1997, and the town's Duke's Festival was staged in his memory (its fourth edition ran August 1 to 10, 2000). His last credits are archival: he is the baritone saxophonist on two tracks of Rotondo's RAI-archive CD The Legend (Twilight Music, 2007), among them "Moonlight In Vermont," which also credits Franco Tonani on drums and Mal Waldron on piano.

Marinacci's baritone saxophone belongs to the Rome studio-jazz school of the late 1950s: cool-toned section and solo work in the bands of Rotondo, Umiliani and Trovajoli, alongside American visitors such as Chet Baker. His flute, which he played in C, alto in G and bass, is the voice of his own records, moving from bossa nova (1963) to harp-and-vibes jazz (1965) to the modal jazz-funk of Atom Flower's (1972). The Conca Peligna biography says he moved away from the musical soul of the spirituals to give jazz a European one.

Most of his working life was outside the jazz clubs. He was a RAI staff-orchestra musician and a session flutist on film scores, pop records and theme music: he plays on Morricone's Musica Sul Velluto (1964), Gianni Ferrio's Emmanuelle score and the Peppino De Luca and I Marc 4 soundtrack L'Uomo Dagli Occhi Di Ghiaccio (1971). Discogs nevertheless carries the Jazz genre tag on 54 of the 62 entries it lists under his name, and his own leader records are filed as jazz apart from the 1970 library LP.