"Before You Walk Out of My Life" earned generally favorable reviews upon its release and has since been considered to be one of Monica's signature songs.
Music Week rated the song four out of five, adding, "This 15 year old from the
Whitney and
Brandy school of crooning turns in an ultra-smooth, ultra appealing
R&B ballad which has been top three in the US." Tony Farside from the magazine's
RM Dance Update gave it five out of five, calling it "one of the best new r&b tracks around for a while." He described the song as "a mid to low tempo smoocher with an acappella-ish intro and a lazy beat", and concluded, "A grower and definitely another hit waiting to happen for Monica." Another editor,
James Hamilton deemed it a "sultry" and "attractive" R&B ballad. Christian Hoard from
The Rolling Stone Album Guide called the song a "soppy MOR ballad" that was not playing "to her strengths." In a retrospective review of the song,
Singersroom editor Erica Henderson felt that "the track features a heartfelt vocal performance from Monica, as she pleads with her lover not to leave her. The song's catchy melody and relatable lyrics made it an instant hit, with its memorable chorus and powerful vocals [...] "Before You Walk Out of My Life" continues to be a standout moment in Monica's discography." Grant Rindner from
Oprah Daily described the record as "another simmering love song dressed up like a mellow rap record filled with DJ scratches."
Park Jin-young called the "perfectly written" and further noted: "It was my ultimate role model as songwriting: a song with a strong beat that was good enough as a ballad." During her
Verzuz battle with
Brandy in August 2020, Monica cited the song as "one of her favorites to sing to this day." ==Chart performance==