"God Only Knows" was first released on May 14, 1966, as the opening track of side two on "Pet Sounds". In its review of the album, "Disc & Music Echo" referred to the song as "a standard gem with its hymnal feel." Norman Jopling of "Record Mirror" decreed that it had "a rollicking salvationist flavour but isn't going to convert anyone." Spencer Davis, frontman of the Spencer Davis Group, praised the song as the album's "most fantastic track" for a contemporaneous survey conducted by "Melody Maker". At the suggestion of Johnston, Tony Rivers and the Castaways recorded a version of the song, which was issued about a week before the Beach Boys released their version as a single.