In a captivating contest, Siyanda Xulu and Hendrick Ekstein struck in extra time after 90 minutes produced a 3-3 stalemate at FNB Stadium.
Maritzburg took a 2-0 lead into the break via goals from Kurt Lentjies and United debutant Tamsanqa Teyise.
Man of the Match George Lebese then hit a quick-fire brace either side of a Bernard Parker long-range effort, before Amakhosi's marquee signing Xulu scored an 83rd minute own goal on debut.
Xulu, however, responded with an acrobatic finish in the 114th minute, with rising talent Ekstein - who is profiled in the latest KICK OFF Magazine - securing the result six minutes later in Steve Komphela's first test as Chiefs coach against his ex-employers.
The Glamour Boys joined Bloemfontein Celtic, Bidvest Wits and Ajax Cape Town in the next round of the season-opening showpiece.