"When Christmas Comes" is a song by American singer-songwriter Mariah Carey with John Legend, released as a digital download on November 21, 2011. The track was originally included on Carey's thirteenth studio album, Merry Christmas II You (2010), then was re-recorded as a duet with John Legend and released a year after. The song was written by Carey and James Poyser.

Scott Shelter of Pop Crush gave the song a 4 out of 5 star rating, describing the duet as "sultry" and "hard to find fault with the holiday duet from two of pop music’s most powerful vocalists". He also praised Carey's ability to write "festive songs for the season". Additionally, Shelter complimented Carey's vocals, stating that "listeners are treated to notes from the upper reaches of Mariah’s five-octave range, which she rarely shows off any more."