Arum used his education and business savvy to become a boxing promoter, and during the 1980s became a driving force behind the sport, rivalling Don King. Arum put together super fights like Marvin Hagler vs. Roberto Duran and Hagler-Thomas Hearns, and while his wealth grew during that time, he was able to gain his boxers' trust by being a honest man who never stole money from his boxers. Many of Arum's boxers and former boxers nowadays can enjoy the fruits of their work because of that, and they have publicly recognized that every penny they made always showed up in their bank accounts.
A particularly touching moment happened when Arum mounted the Hagler-John Mugabi, Hearns-James Shuler double header in Las Vegas April of 1986. After the Hearns-Shuler fight, Shuler, who had lost by knockout in the first round, showed up at Arum's hotel room to thank him for the opportunity to fight Hearns. 10 days later, Shuler was dead in an unfortunate motorcycle accident.
On the first week of January, 2004, FBI agents raided Arum's Top Rank office in Las Vegas. Arum was on vacation when his office was raided, and the FBI originally declined to comment on the raid, but on January 9, news ran across the sports world that the FBI is investigating allegations that Top Rank was involved in fixing the rematch between De La Hoya and Shane Mosley. The investigation puts Top Rank involved in judge bribery to score the fight for Mosley, something that Mosley and his handlers may or may not have been aware of. The federal agency has also announced that it is investigating some Butterbean fights, alongside the Jorge Paez-Verdell Smith fight. It is expected that other fights and fighters will be named soon by the agency. In each of the investigated fights, the winner seems to have been unaware of a fix, if that was the case.
Arum is a member of the International Boxing Hall Of Fame.