In the song, Mitchell ruminates on the recent breakup of a romantic relationship. Christmas is nearing, and Mitchell longs to escape her emotional bonds, openly wishing "I wish I had a river / I could skate away on", a river so long she "would teach my feet to fly." Furthermore, Mitchell's Canadian past is reflected upon, as her current warm (presumably Californian) climate does not offer her that ice or that chance. It is used in the 2000 film Almost Famous, the 2003 film Love Actually and in episodes of Alias, thirtysomething, The Wonder Years, Ally McBeal, New Girl and ER. There are also numerous discussions of Mitchell's songs by Tom Hanks and Meg Ryan in the 1998 movie You've Got Mail.
Keeping with the Christmas theme of the lyrics, the arrangement of the song on Blue (and on many other covers of the song) starts with a theme reminiscent of "Jingle Bells", and this theme figures several times throughout the accompaniment.
Although merely set near Christmas time, rather than being about Christmas, the song has become something of a modern Christmas standard. "River" is the second-most widely covered of songs in Mitchell's oeuvre (432 recordings, behind only "Both Sides, Now"), frequently appearing on albums of Christmas music by pop, folk and jazz artists.