Karlovic, 37, beat the previous best of 49 aces for one match in New York served up by Richard Krajicek in his quarter-final loss to Yevgeny Kafelnikov in 1999.
“I knew there were a lot of aces because there was a period (in the second set) when almost every serve was an ace. I knew there was a lot but I didn’t know it was this many,” said 6ft 11in (2.11m) Karlovic.
Karlovic had three times previously served more than 50 aces in a tournament — his previous best in a tour match was 55 against Lleyton Hewitt in 2009 at the French Open.
In the same year, he served 78 aces against the Czech Republic’s Radek Stepanek in a Davis Cup clash.
He has now served 11,277 aces in his career, 1000 more than second-placed Goran Ivanisevic.
“Of course this is my best shot. I have worked a lot on it. I’m proud of it,” said Karlovic.
America’s John Isner holds the all-time Grand Slam record of 113 aces served during his famous 70-68 fifth-set victory over Nicolas Mahut in the first round of Wimbledon in 2010.