The Bankers Life Fieldhouse in Indianaoplis announced the news minutes before Cardi was scheduled to take the stage, informing fans the show was cancelled and will be rescheduled for September 11.
The "Press" rapper was supposed to perform at 7 PM.
Sources directly connected to Cardi told The Blast a threat was made to Cardi B's safety, and officials made the call to scrap the performance.
The postponement was announced about 40 minutes before the concert was set to begin, and some fans are upset over the last minute notice.
"20 minutes before the show was supposed to start tonight and you CANCEL!!! Come on now," one angry fan tweeted.
Some thought the cancellation had something to do with Cardi sitting down with Bernie Sanders on Monday for a political discussion, especially with the debates of the Democratic party presidential candidates airing tonight.
"Can’t believe i sat in traffic for 2 1/2 hours just to walk in and have the concert cancelled. @iamcardib i get you want to people to get involved in politics but 30 minutes before the concert starts you cancel so people can watch the debate," a fan wrote.