Note that the lines of the first two versions were not exclusive of one another and were often interchanged without preference. Various other versions remove or replace certain Fa la la lines with harp melodies. Sometimes the third, "New Year", version is a follow up.

Note: in this version the third line of "Fa la la" is sometimes interpreted as "Fa, la la la, fa la la la" (Refer to Carols for Choirs 3)

The tune is that of an old Welsh air, first found in a musical manuscript by Welsh harpist John Parry Ddall (c. 1710–1782), but undoubtedly much older than that. The composition is still popular as a dance tune in Wales, and was published in the 1784 and 1794 editions of the harpist Edward Jones's Musical and Poetical Relics of the Welsh Bards. Poet John Ceiriog Hughes wrote the first published lyrics for the piece in Welsh, titling it "Nos Galan" ("New Year's Eve"). A middle verse was later added by folk singers. In the eighteenth century the tune spread widely, with Mozart using it in a piano and violin concerto and, later, Haydn in the song "New Year's Night."

Originally, carols were dances and not songs. The accompanying tune would have been used as a setting for any verses of appropriate metre. Singers would compete with each other, verse for verse — known as canu penillion dull y De ("singing verses in the southern style"). The church actively opposed these folk dances. Consequently, tunes originally used to accompany carols became separated from the original dances, but were still referred to as "carols". The popular English lyrics for this carol are not a translation from the Welsh. The connection with dancing is made explicit in the English lyrics by the phrase "follow me in merry measure" as "measure" is a synonym for dance. A collection of such sixteenth and seventeenth century dances danced at the Inns of Court in London are called the Old Measures. Dancing itself having been previously suppressed by the church was revived during the renaissance beginning in fifteenth century Italy .

During the Victorian re-invention of Christmas it was turned into a traditional English Christmas song. The first English version appeared in The Franklin Square Song Collection, edited by J.P.McCaskey in 1881. See here for a more detailed summary of what various sources say about its history.

An adaptation of "Deck the Halls" was recorded by country music group SHeDAISY that was made for their Christmas studio album Brand New Year and was featured in the Disney animated film Mickey's Once Upon a Christmas. The music video features scenes of the movie. The single was released on November 9, 1999.