Cardi B was born Belcalis Almanzar on October 11, 1992, in The Bronx borough of New York City. She was raised in the Highbridge neighborhood of the South Bronx. She was born to a Dominican father and Trinidadian mother. She spent much time at her paternal grandmother's home in Washington Heights, which she credits with giving her "such a thick […] accent.". As a youth, Cardi B was a member of the Bloods, and has said she was a gang member since the age of 16. She went on to attend Renaissance High School For Musical Theater & Technology, a small specialty school on the Herbert H. Lehman campus.

In 2013, Cardi B began to gain publicity due to several of her videos going viral on social media, on Vine and her official Instagram page.

AllMusic Editor David Jeffries called Cardi B "a raw and aggressive Rapper in the style of Lil' Kim and Foxy Brown." Stereogum called her voice "a full-bodied New Yawk nasal bleat, the sort of thing that you've heard if someone has ever told you that you stupid for taking too long at swiping your MetroCard." They continued to call her voice "an unabashedly loud and sexual fuck-you New York honk—that translates perfectly to rap." In a 2017 Complex article about her, the Editor wrote "unapologetic does not begin to describe the totally unfiltered and sheer Cardi B-ness of Cardi B's personality. She's a hood chick who's not afraid to be hood no matter the setting. Cardi B is Cardi B 24/7, 365, this is why she resonates with people, and that same Energy comes out in her music."

She appeared on the December 9, 2015 episode of Uncommon Sense with Charlamagne. On April 6, 2016, she was on the twelfth episode of Khloé Kardashian's Kocktails with Khloé: In it, she revealed how she told her mother that she was a stripper. In November, it was announced that she would be joining the cast of the BET series, Being Mary Jane. TVLine describes her character, Mercedes, as a "round-the-way beauty with a big weave, big boobs and a big booty to match her oversized, ratchet personality."

In 2015, Cardi B joined the cast of the VH1 reality television series Love & Hip Hop: New York, debuting in season six. She is considered the breakout star of the show's sixth season. The sixth and seventh seasons chronicle her rise to stardom and her turbulent relationship with her incarcerated fiancé. On December 30, 2016, after two seasons, she announced that she would be leaving the show to further pursue a career in music.

Cardi B received her first two nominations at the 2017 BET Awards. In September 2017, the nominees for the annual BET Hip Hop Awards were unveiled, revealing Cardi B to be in the lead, alongside DJ Khaled and Kendrick Lamar, with nine nominations, winning five. She received two nominations at the 60th Grammy Awards: Best Rap Performance and Best Rap Song for "Bodak Yellow". She has won two iHeartRadio Music Awards.

Cardi B's younger sister, Hennessy Carolina, also has a strong following on social media and has accompanied her to award shows, such as the 2017 Grammy Awards. On April 7, 2018, Cardi B revealed her pregnancy on Saturday Night Live; she is having a baby with fiancé Offset.