Lyrically, the song addresses borderline personality disorder at its emotional brink, examining the mental-health side effects of an unrequited love.

[4] The song is built upon ticking hi-hat pattern which Norwood described as a "magical, kind of a dark beat" that Camper had created for B7.

"[10] Jennifer Gonsalves for MEA Worldwide wrote that the album felt "like an out-of-body experience, with Brandy's whispery vocals being the magic carpet that gently guides you through a journey from pain and loss to self-discovery and love," specifically picking out "Borderline" as "probably one of the best representations of this form of storytelling.

[16] Less impressed, Clash editor Robin Murray stated in his review for parent album B7 that "Boderline" was "no more than nice – pleasing on the ear, tugging at the heartstrings, but fail[s] to match the gravitational pull of the record's true highlights".

[17] AllMusic editor Andy Kellman ranked the song among the album's highlights along with "Rather Be", "Lucid Dreams", Borderline", "Say Something" and "Baby Mama".

[19] Filming took place at the vintage-style Parlour Room bar at Yucca Street in the Hollywood neighborhood of Los Angeles, California in July 2020.

[5] Due to the ongoing COVID-19 pandemic in the United States, the video was shot socially-distanced, with a doctor on-set regularly testing people's temperatures.

[5] The nightclub scenes in the video were inspired by Diana Ross's portrayal of singer Billie Holiday in the biographical drama film Lady Sings the Blues (1972).

[19] The video sees Norwood performing "Borderline" in a nightclub, intercut by scenes in which she is forced into a straight-jacket and padded room, representing a psychiatric facility.

"[5] Norwood sang along when the track was played as part of her Verzuz battle against fellow R&B singer Monica on August 31, 2020 at Tyler Perry Studios in Atlanta, Georgia.