While at St Albans School, he met Paul Atkinson and Hugh Grundy. The three joined with Colin Blunstone and Chris White to form The Zombies. As a child he sang as a boy chorister in St Albans Cathedral Choir.
In addition to playing piano and keyboards in the group, Argent was (with White) one of the group's two main songwriters, penning the hits "She's Not There", "Tell Her No", and "Time of the Season", amongst others.
Argent was initially the group's lead singer, with Blunstone on guitar. When Argent's keyboard talents became apparent, he became the group's full-time keyboard player, conceding the role of lead singer to Blunstone.
After The Zombies split, he went on to form Argent, who had a hit album in 1972 with All Together Now, which contained the single "Hold Your Head Up". They also recorded the original version of the rock anthem "God Gave Rock and Roll to You", written by lead singer Russ Ballard, which was later covered by other artists, including Petra and KISS. Argent's first album included the song "Liar" (also composed by Ballard), which became a hit for Three Dog Night.
In 1978, he released solo album 'Moving Home' with many well-known musicians, including Genesis drummer Phil Collins and Weather Report bassist Alphonso Johnson.
Argent later played keyboards with many other musicians, including piano on the title track of The Who's album Who Are You and on Variations with Gary Moore, Julian Lloyd Webber and Andrew Lloyd Webber. In 1986 he composed the theme music for ITV's coverage of the 1986 World Cup, "Aztec Gold". It was released as a [single under the title of "Silsoe". Argent also composed the theme music to the ITV (LWT) sitcom The Piglet Files, which aired from 1990 to 1992. He also played keyboards on and produced Joshua Kadison's 1993 album Painted Desert Serenade.
In 1999 Argent recorded a solo piano album, Rod Argent Classically Speaking, in which he played Chopin études and music by Ravel, Bach and Grieg, as well as three of his own compositions.
Argent and Blunstone have continued to perform together, and in 2004 they recorded a new album, As Far as I Can See, in the style of the Zombies. Subsequent album and DVD Colin Blunstone & Rod Argent of The Zombies Live at the Bloomsbury Theatre received favorable reviews, as did their 2007 US tour. One critic noted, "The Zombies, still led by original keyboard wizard Rod Argent and featuring the smoked-silk vocals of Colin Blunstone, is the best 60s band still touring which doesn't have Mick Jagger as a front man".
In 2006, Argent joined Hamish Stuart, Richard Marx, Billy Squier, Edgar Winter, and Sheila E. touring with Ringo Starr & His All Starr Band.