Originally from San Cipriano d'Aversa in the Province of Caserta, Bardellino was an important Cosa Nostra affiliate in the region of Campania. "Bardellino was the reference point of all Camorra clans, even the ones that could not stand him. With his charisma he managed to maintain a certain equilibrium in Campania", according to the pentito Pasquale Galasso. He was the founder of the Casalesi clan, around which for almost a decade moved a united confederation of families (Schiavone, Bidognetti, Zagaria, Iovine, Venosa) rooted in a large territory which extended from southern Lazio through the agro aversano (countryside near Aversa), to Naples.
He had close and powerful contacts within the Sicilian Mafia, initially with the Porta Nuova family of Pippo Calò. He was one of the few Camorra bosses who were also initiated in Cosa Nostra. Together with Lorenzo Nuvoletta and Michele Zaza he was sworn in to seal a pact on cigarette smuggling in 1975.
In contrast to the Nuvoletta brothers who were allied with the Corleonesi headed by Luciano Leggio and Salvatore Riina, Bardellino was allied with Rosario Riccobono, Stefano Bontade, Gaetano Badalamenti, and Tommaso Buscetta, all heads of fallen Palermo families which were defeated by the Corleonesi in the Second Mafia War, and forced to flee.
It is believed that Antonio Bardellino was the initiator of the Casalesi clan in the area of Casal di Principe and San Cipriano d'Aversa, especially due to the transformation he implemented within the clan. The rituals of affiliation remained as well as the rate of murders, but the leap in quality was the continued infiltration of the legal capitalist economy with the proceeds of illicit drug trafficking. This was favoured by the 1980 Irpinia earthquake and the subsequent reconstruction, that prompted the families to create a consortium for their companies that performed the work of earth-moving, building houses and roads. Another factor was the great entrepreneurial ability of Bardellino himself. He owned an import/export firm of fish meal together with other clans, which in fact covered up a cocaine smuggling operation from Brazil to Italy. Besides trafficking cocaine trade, he was involved in the heroin trade with Lorenzo Nuvoletta and Ciro Mazzarella, supplying the Sicilian Mafia.
In the 1980s, Bardellino realized that cocaine, not heroin, would become the more profitable drug and organized a trafficking operation smuggling it from Latin America to Aversa via a fish flour import-export business. Heroin was smuggled as well, and shipments to the Gambino crime family were concealed inside espresso filters. When one shipment was intercepted by the authorities, Bardellino reportedly called John Gotti and told him; "Don't worry, now we're sending twice as much the other way".