Wonderland, which will be the star's third holiday album, joins an already packed Christmas box of releases from the likes of Loretta Lynn, She & Him, Jennifer Nettles, Rascal Flatts, Neil Diamond, and Kacey Musgraves.
The project features 13 "traditional and contemporary holiday classics", including new takes on Silver Bells, Angels We Have Heard on High, Away in a Manger, and Canada's oldest festive song, Huron Carol.
Sarah also tackled Randy Newman's winter tune Snow for the project and worked with the Bulgarian Symphony Orchestra on four tracks.
Country star Harris and Martha Wainwright joined her in the studio for a new version of Go Tell it On the Mountain.
MCLachlan's previous holiday releases were Wintersong in 2006 and last year's (15) The Classic Christmas Album.