In video footage obtained by TMZ, an unidentified individual was seen being repeatedly kicked and punched outside of the Mark Hotel in the early hours.
Law enforcement sources revealed that the incident stemmed from the fan trying to get an autograph from the pregnant star, which she refused.
The video sees a persistent male yell: 'I'm an autograph hound' before three security guards pushed him to the ground and started attacking him.
Following the beatdown, further video footage showed the victim being transported to the hospital via ambulance at 2.30am, where he was treated for back and neck pain.
MailOnline has contacted representatives for Cardi for further comment.
Meanwhile, Cardi looked absolutely ecstatic to attend her very first Met Gala earlier on in the evening.
The mum-to-be looked fabulous in a pearl and jewel-encrusted Jeremy Scott gown which hugged her pregnant curves as she arrived at the Metropolitan Museum of Art in New York.
The dress featured a thigh-high slit and a billowing ballgown silk skirt for extra drama.
