After leaving an Irish showband, Morrison returned to his hometown of Belfast, where he joined up with guitarist Billy Harrison, bassist Alan Henderson and keyboardist Eric Wrixon and formed the band that would eventually become Them.

Noted for its bossa nova and calypso beats, "One Two Brown Eyes" has often been considered "proto-psychedelic" by critics, largely owing to Harrison's performance, where he emulated a slide guitar using a thimble.

[2][3] After responding to an advert published in the Belfast Telegraph for musicians to play at a newly opened rhythm and blues club at the Maritime Hotel, Morrison got acquainted with guitarist Billy Harrison, bassist Alan Henderson alongside keyboardist Eric Wrixon; after drummer Ronnie Milling joined the band, Wrixon was inspired by the name Them, based on the movie of the same name.

[5] Writer Clinton Heylin believes that "One Two Brown Eyes" largely originated from jam sessions the band held at the Maritime Hotel, though notes that the lyrics may have been written as early as the summer of 1963, when Morrison composed "Gloria".

[10][11][nb 2] At that point, Them consisted of Morrison (vocals, harmonica), Harrison (guitar), Henderson (bass), Ronnie Milling (drums) and Pat McAuley (keyboards).

[16] "Other notable songs recorded by Them included the tribal, proto-psychedelic pulse of "One Two Brown Eyes" on which guitarist Billy Harrison used a thimble to get a bottle-neck slide sound."

[18] Multiple authors note the song's sparse instrumentation that largely surrounds the bossa nova beats played by Millings and Graham.

[19] They tell the story of the narrator stumbling upon a subject with "two hypnotizing brown eyes" that has told lies about Morrison; he reprimands them by "humbling them through cutting them down to his size".

[22][23] On 4 September 1964, Decca released "Don't Start Crying Now" as Them's debut single in the UK, coupled with "One Two Brown Eyes" on the B-side.