It began as a solo album by Kenny Loggins; Jim Messina was with Columbia Records, serving as an independent producer when he met Loggins. In the course of producing Loggins' work, Messina provided backing vocals and guitar, leading to the album's full title, Kenny Loggins with Jim Messina Sittin' In.
MFSL released an audiophile version of Sittin' In on the label's silver disc series in 1989. In 1994, Columbia Records' Sony Mastersound division also did their own remastering and released it as a gold CD. A new remastering by Kevin Gray was released as a vinyl-only pressing on 180gram audiophile vinyl by Friday Music on May 10, 2011.