Produced by Swizz Beatz and Dr. Dre, the song showcases a musical departure from the previous singles by the singer, with a more upbeat sound led by drums and percussion, as opposed to her classical R&B sound.
Rapper 50 Cent has a version of the song with one verse by Dr. Dre and the hook by Alicia Keys, also called "New Day".
On the song, Keys sings about "touching the sky and not letting chances go to waste". It received praise from music critics, who complimented the new musical direction, as well as criticizing the downgrade of Keys' "powerhouse voice" in favor of percussion.
"New Day" is a contemporary R&B song with house, hip hop, pop and reggae influences, and a duration of four minutes and four seconds, which was produced by Keys' husband Swizz Beatz.
Jenna Hally Rubenstein from MTV noted that the song is "clearly inspired" by the experiences and feelings the singer had about her son, Egypt.