The "Bodak Yellow" artist, 24, became the first female rapper to score a solo No.1 in the US since Lauryn Hill achieved that feat with "Doo Wop (That Thing)" in 1998.
Celebrating her achievement at her label Atlantic Records in New York, she thanked her friends and family for supporting her
A video acquired by TMZ shows the former Love & Hip Hop: New York star, whose real name is Belcalis Almanza, say: "I'm very happy, I'm very honoured. You know who your real friends is when you open a business. I've experienced that this week.
"Because all my friends, everyone I grew up with, everybody posted so I could go to No. 1, without me even asking. They did it every day, just harassing their followers."
She then apparently began to sing a cheeky rendition of Taylor Swift's song "Look What You Made Me Do".
Fellow rapper Nicki Minaj, who was denied a No.1 spot in 2014 with "Anaconda" due to Swift's three-week reign with "Shake It Off", congratulated Cardi B by tweeting: "Congratulations to a fellow NEW YAWKA on a RECORD BREAKING achievement. Bardi, this is the only thing that matters!!! Enjoy it @iamcardib," she wrote.
Culture writer Ira Madison III noted in the Daily Beast: "'Bodak Yellow' is [also] refreshing in its candidness. Cardi doesn't shy away from her past... instead using it to demonstrate how far she's come. It's become an anthem for a reason: it's an aspirational song about taking on haters and flourishing, with Cardi rapping: 'Don't give a f*** about who ain't fond of me'...
He added: "And while the apolitcal Swift has mostly remained silent during this turbulent summer, allowing the music to promote itself, Cardi has been front and centre, calling out the NFL for not hiring quarterback Colin Kaepernick and lashing out at 'Carrot Face' Trump for ignoring the devastation in Puerto Rico(born Belcalis Almanza, Cardi is Afro-Latina and recorded a Spanish version of 'Bodak Yellow'."
Cardi tweeted after the news was announced: "Every single FEMALE RAPPER CONGRATULATED ME TODAY. Is the best feeling cause I listened to ALL OF THEM."