The song uses a moon motif, which Young has mentioned as being very important to him and having quasi-religious undertones. It is a tribute to his wife Pegi Young, and the two are dancing in a bar in the music video. Linda Ronstadt provides the backing vocals. According to the sheet music published at Musicnotes.com by Sony/ATV Music Publishing, the song is composed in the key of D Major with Young’s vocal range spanning from D3 to F#4.
Rolling Stone ranked “Harvest Moon” as the #37 all time Neil Young song. Allmusic’s Matthew Greenwald strongly praised the song, stating that the song epitomized the album and “the power of nature and music, as well as a feeling of celebrating lifetime love are the focal points here, and Young captures it all in his typically literate, artless style.” Greenwald praised the melody as “positively gorgeous, and it’s one that could have easily framed a heavier song.” “Classic Rock Review” called it an “absolute masterpiece of a title song” that “celebrates longevity in relationships and love affairs with a flawless melody backed by a perfect music arrangement.” They went on to say that “from the upfront acoustic riffing to the picked steel guitar, subtleties of ethereal sounds, soft brush strokes on the drums, and beautiful background vocals, this song captures the essence of beauty and romance as well any song ever.”