In the 1960s, while associated with the UK rock band The Presidents (band), Johns began working as a recording studioengineer at IBC Studios, Portland Place, London and was able to take the band in during weekends and try his skills at production and recording. The Presidents was his first true production work. In 1969, Johns was called upon to rescue the troublesome Get Back sessions for The Beatles. Johns compiled several versions of the album, which were all rejected by the band, before the project was eventually turned over to producer Phil Spector. Spector's version became the released album, which was retitled Let It Be.
Johns' subsequent work on the first three albums by the Eagles was fundamental in establishing the group's sound and style. He also mixed a 5.1 SACD version of the Eric Clapton album Slowhand at Sphere Studios.
In 2011, after a couple of decades spent largely away from production, Johns worked with Ryan Adams on his album, Ashes & Fire. In February 2012, Johns began work on the Band of Horses album, Mirage Rock. In a nod to Johns' work with the Faces, the credits contain the note: "Thanks to difference, you made all the Glyn."